OBD-II Code P1451: EVAP System Vent Control Circuit Malfunction

What Does P1451 Mean?

The P1451 code signifies your car's Powertrain Control Module (PCM) detected an electrical fault in the EVAP system's vent solenoid circuit. The EVAP system traps gasoline vapors and directs them into the engine to burn. This code means the vent valve is not responding electrically, compromising the system's ability to manage fuel vapors and test for leaks.

Technical definition: The SAE/OBD-II definition for P1451 is "Evaporative Emission Control System Vent Control Valve Circuit Malfunction." On many Ford, Lincoln, and Mercury vehicles, it is defined as "Unable to Bleed Up Fuel Tank Vacuum." This means the PCM detected the electrical signal to or from the vent solenoid is outside its expected range—indicating an open circuit, short to ground, or a failed solenoid coil.

Can I Drive With P1451?

Yes, But With Caution. Yes, you can drive with a P1451 code, as it does not cause immediate performance or safety issues. However, ignoring it for more than a few weeks stresses fuel tank seals and hoses, leading to expensive repairs. Driving with this code causes an automatic emissions test failure, and long-term neglect (over a month) damages the fuel pump due to pressure imbalances, adding a $500-$1000 repair cost.

Common Causes

• Faulty EVAP Canister Vent Solenoid (Very Common) — The solenoid fails internally, gets stuck, or its coil burns out. Corrosion from road salt and moisture is the primary factor in colder climates.
• Damaged Wiring or Electrical Connector (Very Common) — Exposed wires under the vehicle break, corrode, or short out. On Ford trucks, the harness rubs against the frame or spare tire, severing the connection.
• Clogged EVAP Vent Tube, Filter, or Canister (Common) — Insects, mud, or road debris clog the vent tube, filter box, or charcoal canister. This physical blockage prevents airflow, tricking the PCM into logging an electrical failure.
• Faulty Fuel Tank Pressure (FTP) Sensor (Common) — The FTP sensor sends incorrect pressure data to the PCM. This misleads the computer into thinking the vent valve failed, triggering a P1451 even if the valve and wiring are perfect.
• Blown EVAP System Fuse or Relay (Less Common) — A blown fuse cuts power to the vent solenoid, immediately triggering a circuit code. Always check the fuse box before replacing expensive components.
• Overfilling the Fuel Tank (Less Common) — Topping off the fuel tank forces liquid gasoline into the charcoal canister. This saturates the charcoal, sending debris into the vent solenoid and jamming it.
• Loose or Faulty Gas Cap (Rare) — A poorly sealed gas cap disrupts EVAP pressure regulation. On sensitive systems, this confuses the PCM and contributes to a P1451 code.
• Faulty Powertrain Control Module (PCM) (Very Rare) — The driver circuit within the main computer fails. Consider this only after exhaustively testing wiring, solenoids, sensors, and fuses.

Symptoms

• Check Engine Light is On — This is the most common and often the only symptom. The light stays on until you repair the fault.
• Failed Emissions Test — An active P1451 code indicates a primary emissions control system fault, resulting in an automatic failure of state-mandated inspections.
• Hissing Sound or Difficulty Removing Gas Cap — Removing the gas cap releases a prominent 'whoosh' of trapped pressure or vacuum. A strong vacuum makes the cap difficult to twist off.
• Hard Starting After Refueling — A stuck-closed vent solenoid builds pressure in the fuel tank, forcing excess vapor into the engine during refueling and causing a rich condition.
• Fuel Smell — You notice a faint gasoline odor near the rear of the vehicle as unregulated vapors escape the malfunctioning EVAP system.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Replace EVAP Canister Vent Solenoid — Parts: $40-$150, Labor: $100-$250, ~1.5 hr book time (Intermediate)
• Repair Damaged Wiring or Connector — Parts: $15-$50, Labor: $150-$300, ~1.5 hr book time (Intermediate)
• Clean/Replace EVAP Vent Tube or Filter — Parts: $10-$60, Labor: $100-$150, ~0.8 hr book time (DIY)
• Replace Charcoal Canister — Parts: $200-$500, Labor: $125-$250, ~1.5 hr book time (Intermediate)
• Replace Gas Cap — Parts: $15-$40, Labor: $0, ~0.1 hr book time (DIY)

DIY vs Professional

• Replace Gas Cap — Beginner:
  Tools: None
• Clean/Replace EVAP Vent Tube or Filter — Beginner:
  Tools: Safety glasses, compressed air source, screwdrivers/pliers.
• Replace EVAP Canister Vent Solenoid — Beginner:
  Tools: Jack and jack stands, socket set, pliers, safety glasses.
• Repair Damaged Wiring or Connector — Beginner:
  Tools: Multimeter, wire strippers, soldering iron or quality butt connectors, heat shrink tubing, electrical tape.
• Replace Charcoal Canister — Beginner:
  Tools: Jack and jack stands, socket set, hose clamp pliers, safety glasses.

Used vs. New Parts: Buying Guide

When a used part is worth it: A used charcoal canister from a low-mileage vehicle offers significant savings. For the vent solenoid, the low cost of a new aftermarket part makes buying used too risky.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the donor vehicle part number is an exact match.
• Avoid parts from regions with heavy road salt use.
• Ask the seller if the donor car had any emissions-related codes.

Decision logic:

• If Part is an electrical solenoid and costs < $150 new → Buy new; the risk of a used part failing isn't worth the small savings.
• If Part is a charcoal canister and the vehicle is > 10 years old → A used part from a low-mileage donor is a reasonable, budget-conscious choice.
• If You live in a state with strict annual emissions testing → Favor new parts with a longer warranty to avoid repeat repairs and test failures.

Warranty tradeoff: Used parts offer a 30-90 day warranty. New aftermarket parts come with a 1-year to limited lifetime warranty. New OEM parts carry a 1-2 year warranty.

Worst-case if a used part fails: $200-$450 if a used part fails after installation, accounting for repeat labor charges.

What Happens If You Wait — Timeline

1. 0-1 month: Code is set and Check Engine Light is on. The vehicle automatically fails any OBD-II emissions test. No drivability symptoms are noticeable. (MPG impact: 0-2%% · Added cost: $0)
2. 1-3 months: Sustained incorrect pressure stresses seals in the fuel tank and EVAP hoses. A faint fuel odor is present after driving. (MPG impact: 1-3%% · Added cost: $20-50 in wasted fuel.)
3. 3-6 months: The charcoal canister becomes saturated and ruined. Stressed hoses develop small cracks, leading to new leak codes (P0442/P0455). (MPG impact: 2-5%% · Added cost: $300-$600 (to replace a ruined charcoal canister).)
4. 6+ months: Chronic pressure imbalance affects the fuel pump's longevity. Unburned vapors shorten the life of the catalytic converter. (MPG impact: 3-7%% · Added cost: $500-$2000+ (to address secondary damage to the fuel pump or catalytic converter).)

Cost of Not Fixing It

• 0-1 month: Guaranteed emissions test failure. Minor decrease in fuel economy (1-2 MPG). (Added cost: Negligible, other than a failed test fee.)
• 1-6 months: Sustained pressure stresses fuel tank seals and hoses, causing new leaks. Liquid fuel saturates and ruins the charcoal canister. (Added cost: $300-$600 (for a new charcoal canister and hoses).)
• 6+ months: Chronic EVAP system failure contributes to premature failure of the catalytic converter due to incorrect vapor management. (Added cost: $800-$2000 (for catalytic converter replacement).)

Diagnosis Steps

1. Inspect the Gas Cap
   Turn off the engine. Remove the gas cap and inspect its rubber seal for cracks or damage. Ensure it clicks at least three times when tightened.
   Tools: None (Beginner)
2. Visually Inspect the EVAP System
   Safely raise the vehicle. Locate the charcoal canister and vent solenoid near the fuel tank. Look for cracked hoses, mud blockages, or insect nests in the vent hose outlet.
   Tools: Flashlight, Jack and Jack Stands (Beginner)
3. Inspect the Electrical Connector and Wiring
   Unplug the vent solenoid connector. Inspect the pins for green or white corrosion. Trace the wiring harness, looking for areas rubbed bare against the frame or spare tire.
   Tools: Flashlight (Intermediate)
4. Test the Solenoid's Resistance
   Set a multimeter to Ohms (Ω). Touch the probes to the solenoid's electrical pins. A functional Ford solenoid reads 48 to 65 ohms. Infinity (OL) means an open coil; near zero means a short. Replace the solenoid in either case.
   Tools: Multimeter (Intermediate)
5. Check for Power at the Connector
   Turn the ignition to 'On' (engine off). Set the multimeter to DC Volts. Connect the black probe to a frame ground and the red probe to the connector's power pin. You must see battery voltage (~12V).
   Tools: Multimeter, Vehicle-Specific Wiring Diagram (Advanced)
6. Perform a Bi-Directional Scan Tool Test
   Command the vent solenoid to open and close using the scan tool. Listen for an audible 'click'. Simultaneously monitor the FTP sensor data. If it clicks but pressure doesn't change, you have a blockage or bad sensor.
   Tools: Bi-Directional Scan Tool (Advanced)
7. Test the Fuel Tank Pressure (FTP) Sensor Voltage
   With the gas cap removed, back-probe the FTP sensor signal wire. Key on, engine off, it must read ~1.5V on GM or ~2.6V on Ford. 0V or 5V indicates a wiring or sensor fault.
   Tools: Multimeter, Back-Probe Pins, Wiring Diagram (Advanced)
8. Check the Solenoid Control Circuit
   Connect to the vent solenoid's ground-side control wire. When the PCM commands the valve, you must see a square wave or changing duty cycle. A flat line indicates a broken wire or bad PCM.
   Tools: Oscilloscope or Multimeter (with Duty Cycle/Hz) (Pro)
9. Monitor EVAP System Pressure
   Monitor the Fuel Tank Pressure PID in inches of water (inH2O). With the gas cap off, it reads 0 inH2O. During an EVAP test cycle, the system must build and hold a slight vacuum. No pressure change confirms a circuit fault or blockage.
   Tools: Advanced Scan Tool (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 170-210°F (Engine fully warmed up.)
• Fuel Level: 15-85% (Fuel tank neither full nor empty; 1/2 to 3/4 full is ideal.)
• Vehicle Speed: 40-65 mph (Steady highway cruise with minimal throttle changes.)
• Ambient Air Temp: 40-100°F (EVAP monitor suspends testing in extreme hot or cold weather.)

Related Codes

• P0446 — Diagnostic Twin: P0446 is the generic SAE code for "EVAP Vent Control Circuit Malfunction." P1451 is the manufacturer-specific version of the exact same fault.
• P1450 — Close Sibling: P1450 means "Unable to Bleed Up Fuel Tank Vacuum." They point to the same components (stuck vent valve, clogged line) but trigger during different phases of the EVAP self-test.
• P0455 — Symptom vs. Cause: P0455 indicates a large physical leak. A vent solenoid stuck open due to a P1451 fault prevents the system from sealing, logging a P0455 code. Fix the circuit code (P1451) first.
• P0442 — Symptom vs. Cause: P0442 indicates a small physical leak. An intermittently failing vent solenoid causes a poor seal that the PCM interprets as a small leak.

Climate & Environmental Factors

• Cold Climates / Road Salt: Road salt and moisture spray onto the undercarriage, causing severe corrosion on the vent solenoid's electrical connector and body, leading to electrical failure.
• Dusty or Off-Road Environments: Driving in dusty conditions clogs the EVAP system's vent filter or hose outlet. This blockage prevents airflow and triggers a P1451 code.
• Humid Climates / Insect Activity: Spiders and wasps build nests inside the EVAP vent hose outlet, creating a complete blockage that mimics a failed valve.

How to Talk to a Mechanic About This Code

Say this: "I have a P1451 code on my vehicle and I'd like to schedule a diagnostic. Since this is a circuit code, please start by testing the vent solenoid, its connector, and the wiring harness for power, ground, and continuity before recommending any parts. Please also check for any blockages in the vent tube."

This signals to the shop that you understand P1451 is an electrical code and that the most common failures are wiring-related. It directs them to perform a proper diagnosis instead of immediately replacing the most common component.

Avoid saying:

• 'My check engine light is on, can you fix it?' (This is too vague and invites a lengthy, expensive diagnostic process).
• 'I think I need a new vent solenoid.' (This leads them to replace the part without diagnosing the underlying circuit issue).
• 'Just fix whatever is wrong.' (This gives the shop a blank check to replace multiple parts without your approval).

Questions to ask before authorizing the repair:

• What were the results of the electrical tests on the vent solenoid circuit? Did it have power and ground?
• Did you find any corrosion in the connector or chafing on the wiring harness?
• Did you inspect the vent hose and charcoal canister for physical blockages like insect nests or debris?
• Can you show me the damaged part or the corroded connector?
• What is the warranty on the parts and labor for this repair?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended only if the vehicle is under warranty or has a known software-related TSB. Otherwise, it is not cost-effective.
  Best for: Vehicles under an emissions or bumper-to-bumper warranty., Known manufacturer-specific issues that require a PCM reflash (e.g., Ford TSB 17-0099)., Complex electrical issues that an independent shop failed to diagnose.
  Downsides: Significantly higher labor rates (often 1.5-2x more than independent shops)., Recommends replacing entire assemblies when only one component failed. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit for most P1451 repairs. A competent independent mechanic easily tests the circuit, inspects for wiring damage, and replaces necessary components at a reasonable cost.
  Best for: Out-of-warranty vehicles where cost is a primary concern., Diagnosing common and well-documented codes like P1451., Building a long-term relationship with a mechanic who knows your vehicle's history.
  Downsides: Diagnostic skill and equipment quality vary widely. Vet the shop by checking for ASE certifications., Lacks immediate access to the latest manufacturer TSBs or specialized tools. (Typical cost: +0% vs. baseline)
• Chain Shop: Acceptable for a free code scan, but avoid for the actual diagnosis and repair. P1451 requires more than just replacing a part.
  Best for: Simple, straightforward part replacements like a gas cap.
  Downsides: Technicians lack in-depth diagnostic training for electrical circuit faults., High pressure to meet sales targets leads to upselling unnecessary services., Unable or unwilling to perform detailed wiring repairs. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 40-50% of the car's private-party value, pause and carefully consider your options.

• Car worth $4000, fix is $350: Fix it. This is a relatively minor repair cost compared to the car's value.
• Car worth $2000, fix is $750: Borderline. The repair is nearly 40% of the car's value. Consider if the car has other needs before authorizing.
• Car worth $1500, fix is $750: Walk away. The repair cost is 50% of the vehicle's value. It is not a sound financial decision unless the car is otherwise in perfect condition.

What Scan Tool You Need for This Code

Minimum: A scanner that reads and clears codes, and views live data for the Fuel Tank Pressure (FTP) sensor.

A basic $20 code reader only gives you the P1451 code. To properly diagnose it, you must see if the FTP sensor's readings change when the system is tested. The real diagnostic power comes from bi-directional control.

Budget: BlueDriver Pro (~$99) — Reads the code, provides repair reports, and displays live data for the FTP sensor. It checks EVAP system readiness but lacks bi-directional control to command the solenoid.

Mid-range: Foxwell NT510 Elite (~$180) — Offers full bi-directional control, allowing you to command the vent solenoid to open and close directly from the tool. This determines if the solenoid is mechanically stuck or if the circuit is faulty.

Professional: Autel MaxiCOM MK808S (~$450) — Provides full bi-directional control for all vehicle systems, including comprehensive EVAP system tests. It offers faster processing and graphs live data for professional-level diagnostics.

Rent vs buy: Most auto parts stores offer free code reading, but these are basic readers. For a P1451, which requires bi-directional control to diagnose properly, renting is not viable. Buying a mid-range tool is the most effective choice.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear the P1451 code.
2. Perform a complete EVAP drive cycle to run the system's readiness monitor.
3. Re-scan the vehicle to confirm no codes return.

Drive cycle (~30 minutes): Start with a cold engine. Fuel tank must be 1/2 to 3/4 full. Idle for 2-3 minutes. Drive for 10-15 minutes at a steady highway speed (45-65 mph). Allow the vehicle to cool down and repeat.

Readiness monitors affected: EVAP Monitor, Catalyst Monitor, Oxygen (O2) Sensor Monitor

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Disconnecting the battery clears the code but resets all readiness monitors to 'Not Ready', causing an automatic emissions test failure.
• The code returns within 50-100 miles if the underlying problem remains unfixed.
• Failing to meet specific drive cycle conditions prevents the EVAP monitor from running.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An active P1451 code is an automatic smog check failure. The EVAP readiness monitor must be set to 'Ready' to pass.
• New York: NYS vehicle inspection includes an OBD-II scan. An illuminated Check Engine Light results in an automatic failure.
• Texas: In counties requiring emissions testing, an active P1451 code causes the vehicle to fail the OBD-II portion of the inspection.

Most Commonly Affected Vehicles

• Ford F-150 (2015-2020) — Extremely common due to the EVAP system redesign. Often caused by a faulty bleed solenoid (Part #HC3Z-9C968-A) or a clogged Fuel Tank Pressure sensor (Part #BL3Z-9F972-A), especially on 3.5L EcoBoost and 5.0L models.
• Ford F-150 (1997-2003) — Prone to this code due to the wiring harness rubbing against the frame near the spare tire. A small disc-shaped filter integrated with the vent system also clogs with dust.
• Lincoln Town Car (1998-2004) — Frequently caused by a failed vent solenoid coil due to corrosion from road salt. The solenoid is located above the rear axle.
• Ford Explorer (1999-2005) — The vent solenoid and its wiring, located near the spare tire on the driver's side frame rail, are common failure points. Resistance on a good solenoid is around 30-40 ohms.
• Mazda Tribute, 3, 6 (2001-2016) — On the Mazda 3, the vent hose outlet gets clogged with dust and debris where it terminates inside a frame rail, causing a restriction that mimics a valve failure.
• Subaru WRX (2015-2021) — Owners report this code appearing intermittently. Diagnosis is complex, often requiring the entire canister and valve assembly to be replaced.
• Chevrolet / GMC Silverado / Sierra (1999-2007) — A TSB addresses issues where dust and debris clog the vent system in dusty environments, causing a restriction that triggers a vent circuit fault.
• Nissan Various Models (1996-2009) — P1451 is a known code on various Nissan models from this era, typically pointing to a failure of the EVAP vent control valve circuit.

Manufacturer-Specific Notes

• Ford: The wiring harness for the vent solenoid routes where it rubs against the frame or spare tire, leading to broken wires. TSB 17-0099 for 2015-2016 F-150s notes a PCM software glitch causes a false P1451, requiring a reflash.
• Ram (Cummins Diesel): CRITICAL DISTINCTION: On 2014-2020 Ram 2500/3500 trucks with the Cummins engine, P1451 means 'Diesel Particulate Filter (DPF) System Performance.' It has nothing to do with the EVAP system.
• Volkswagen/BMW: On early 2000s VW and BMW models, P1451 points to damaged wiring for the canister vent solenoid or a fault in the 'Leak Detection Pump' (LDP) circuit.
• Honda: Honda uses P0498 or P0499 for this circuit. If you see P1451 on a Honda, a generic scanner is misinterpreting the code. Use an OEM-level tool to get the correct code.

Real Owner Stories

1999 Ford F-150 4.2L V6

Check Engine Light with P1451 code came on immediately after being reset.

What they tried:

1. Tested the vent solenoid and found correct resistance (62 ohms).
2. Suspected a wiring issue.

Outcome: The owner traced the wiring harness and found a broken power wire under the air filter housing where the harness rubbed on a bracket. Repairing the wire solved the problem.

Lesson: Even if the component tests good, a circuit code points to a wiring failure. Trace the harness for common chafe points before replacing parts.

2001 Lincoln Town Car 4.6L

P1451 code present. Vehicle was in a region with heavy road salt.

What they tried:

1. Initial diagnosis pointed to the vent solenoid.

Outcome: The problem was a corroded electrical terminal inside the connector for the vent solenoid. The owner soldered the terminal directly to the wire to establish a solid connection.

Lesson: In salt-belt regions, the problem is frequently the connector itself. Unplug the connector and inspect the pins for green or white corrosion before ordering a new part.

2001 Ford F-150 5.4L at 180,000 miles

P1451 code persisted after multiple checks and repairs.

What they tried:

1. Replaced the gas cap.
2. Repaired a previously botched wiring repair on the frame.

Outcome: The owner discovered the entire valve was disconnected and flopping loose from the charcoal canister. Re-attaching the valve to the canister resolved the code.

Lesson: A visual and physical inspection is critical. A component can be electrically sound but physically disconnected, causing the system to fail its pressure test.

Mazda with P1451

Check Engine Light on, no other symptoms.

What they tried:

1. Replaced the vent solenoid, but the code returned.
2. Smoke-tested the system but found no leaks.

Outcome: The root cause was a spider's nest completely blocking the EVAP vent hose outlet inside a frame rail. Cleaning out the nest permanently fixed the code.

Lesson: A physical blockage perfectly mimics an electrical failure. Always check that the vent hose outlet is clear of debris or insect nests.

How to Prevent This Code From Triggering

• Avoid 'topping off' the fuel tank. (Every fill-up.) — Forcing liquid fuel past the automatic shutoff saturates the charcoal canister, ruining it and sending debris into the vent solenoid.
• Periodically clean the EVAP vent hose outlet. (Annually in dusty/humid areas.) — The vent outlet is a common place for spiders and wasps to build nests, causing a blockage that mimics a failed valve.
• Apply dielectric grease to under-vehicle electrical connectors. (Whenever connectors are serviced.) — Applying dielectric grease inside the vent solenoid connector creates a moisture-proof barrier, preventing corrosion.
• Inspect the vent solenoid wiring harness. (Annually, during tire rotation or oil change.) — A quick visual inspection catches insulation that rubbed through before the wire breaks, preventing the code from appearing.
• Consider an undercoating service in corrosive environments. (Annually.) — Professional oil-based undercoating protects electrical wiring and components from road salt, reducing corrosion-related failures.

Frequently Asked Questions

I replaced the vent solenoid, but the P1451 code came back. What now?

The problem is almost certainly in the wiring or a related component. Meticulously inspect the wiring harness for chafing or corrosion near the frame or spare tire. Next, test the Fuel Tank Pressure (FTP) sensor for correct voltage readings.

What is the most common misdiagnosis for P1451?

The most common mistake is replacing the vent solenoid without testing the circuit. The actual cause is frequently a corroded connector pin or a wire rubbed through its insulation. Overlooking a faulty Fuel Tank Pressure (FTP) sensor is the second most common error.

Why did my P1451 code come back after I cleared it?

The vehicle's computer runs complex self-tests to verify the EVAP system works correctly. If you clear the code without fixing the root cause, it reappears as soon as the test fails again. This typically happens within 50 to 100 miles of driving.

Is a P1451 repair covered by warranty?

This repair falls under the vehicle's bumper-to-bumper warranty (e.g., 3 years/36,000 miles). It is also covered under the Federal Emissions Warranty, which mandates 2 years/24,000 miles for emissions parts like valves and solenoids. Check with your dealer to confirm specific coverage.

Can a loose gas cap cause a P1451 code?

A loose gas cap is not the primary cause for this specific circuit code, but it contributes on highly sensitive systems. A bad seal disrupts the system's ability to hold pressure, tricking the PCM into assuming a vent valve fault. Always check the gas cap first since it is a free inspection.

Will P1451 affect my car's performance or fuel economy?

You will not notice any difference in how your car drives. A slight decrease in fuel economy of 1 to 2 MPG occurs in some cases, but major performance issues are nonexistent. The primary impact is an automatic failure on vehicle emissions tests.

Where is the EVAP canister vent solenoid located?

It mounts directly on or very close to the charcoal canister underneath the vehicle. The charcoal canister is a black plastic box typically located near the fuel tank or the spare tire.

Key Takeaways

• Verify the vent solenoid's internal coil health using a multimeter; a functional Ford solenoid measures exactly 48 to 65 ohms of resistance.
• Inspect the wiring harness near the spare tire and frame rails first, as chafed wires cause over 40% of P1451 codes on older trucks.
• Test the Fuel Tank Pressure (FTP) sensor voltage before replacing parts; it must read approximately 2.6V on Fords or 1.5V on GMs with the gas cap removed.
• Stop EVAP diagnosis immediately if driving a 2014-2020 Ram Cummins diesel; P1451 on these trucks indicates a clogged Diesel Particulate Filter (DPF).