OBD-II Code P0673: Cylinder 3 Glow Plug Circuit Malfunction

What Does P0673 Mean?

The Powertrain Control Module (PCM) or Glow Plug Control Module (GPCM) detected an electrical fault in the cylinder 3 glow plug circuit. A glow plug acts as a miniature heater to ignite fuel in a cold diesel engine. P0673 triggers when the circuit is open, shorted, or has resistance/voltage outside the manufacturer's expected range.

Technical definition: Cylinder 3 Glow Plug Circuit / Open. The control module detected a lack of current flow or out-of-spec resistance/voltage in the cylinder 3 glow plug circuit. The module flags this fault if the circuit fails its electrical self-test.

Can I Drive With P0673?

Yes, But With Caution. Yes, but expect hard starting in cold climates. The engine runs rough and misfires until warm. Ignoring this risks a no-start condition and incomplete combustion, which damages the Diesel Particulate Filter (DPF) over time—a repair costing over $2,000.

Common Causes

• Defective Glow Plug in Cylinder 3 (Very Common) — The glow plug burned out or its internal resistance shifted out of specification. As a wear-and-tear item, this is the most frequent cause, with a typical lifespan of 60,000 to 100,000 miles.
• Damaged Wiring or Connectors (Common) — The electrical wiring or connector (pigtail) is broken, frayed, loose, or corroded. Constant engine vibration and heat cycles degrade these components.
• Failed Glow Plug Control Module (GPCM) or Relay (Common) — The module or relay switching power to the glow plugs has an internal fault on the cylinder 3 driver. This is a known issue on many Duramax and Ford models.
• Blown Fuse (Less Common) — A fuse within the glow plug circuit blew. This is a secondary failure caused by a short circuit in the wiring or a faulty glow plug drawing too much current.
• Carbon Buildup (Less Common) — Heavy carbon deposits insulate the glow plug, preventing proper cylinder heating and causing removal difficulties. This also degrades the electrical ground connection through the cylinder head.
• Broken Glow Plug Tip (Less Common) — The heating element tip became brittle and broke off into the cylinder. This immediately creates an open circuit and poses a risk of severe internal engine damage.
• Poor Power/Ground Connection at GPCM (Less Common) — A loose or corroded main power feed or faulty ground strap for the GPCM causes erratic voltage, triggering various glow plug codes.
• Faulty Engine Control Module (ECM/PCM) (Rare) — The vehicle's main computer has a failed internal driver circuit for the cylinder 3 glow plug. Consider this only after proving every other component functional.

Symptoms

• Hard Start or No Start in Cold Weather — The engine cranks excessively before starting, or fails to start entirely when cold, because the faulty glow plug is not pre-heating the cylinder.
• Rough Idle on Startup — For the first few minutes after a cold start, the engine runs unevenly, shakes, or misfires because cylinder 3 cannot combust fuel efficiently until the engine builds heat.
• White or Black Smoke from Exhaust on Startup — Excessive white or black smoke billows from the tailpipe immediately after starting. This is unburned diesel fuel expelled from the cold cylinder.
• Check Engine Light On — The PCM detected the circuit fault and illuminated the Malfunction Indicator Lamp (MIL) on the dashboard.
• Glow Plug Indicator Light Flashing or Staying On — The dashboard glow plug light flashes, stays on longer than normal, or refuses to turn off, signaling a system fault.
• Hesitation and Lack of Power — The vehicle hesitates or lacks power before the engine fully warms up due to the single-cylinder misfire.

Diagnostic Flowchart

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

Common Fixes & Costs

• Replace Cylinder 3 Glow Plug — Parts: $20-$50 ($100+ for pressure-sensing type), Labor: $60-$120, ~1.5 hr book time (DIY)
• Replace All Glow Plugs (Recommended) — Parts: $160-$400, Labor: $150-$300, ~2.5 hr book time (Intermediate)
• Replace Glow Plug Control Module (GPCM) — Parts: $150-$300, Labor: $75-$150, ~1 hr book time (Intermediate)
• Repair Damaged Wiring or Connector/Harness — Parts: $10-$40, Labor: $100-$200, ~1.5 hr book time (Intermediate)
• Replace Blown Glow Plug Fuse or Relay — Parts: $5-$30, Labor: $10-$50, ~0.2 hr book time (DIY)

Used vs. New Parts: Buying Guide

When a used part is worth it: Never buy used glow plugs; they are a wear item. A used OEM Glow Plug Control Module (GPCM) from a low-mileage vehicle is a cost-effective alternative to a new OEM part, but carries risks.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the part number matches exactly.
• Check the donor vehicle's VIN history.
• Avoid modules from vehicles with high mileage or electrical issues.

Decision logic:

• If The part is a glow plug → Always buy new. The cost is low and they are a critical wear item.
• If The part is a GPCM and the budget is extremely tight → A used OEM module is preferable to a cheap aftermarket module, which often has compatibility issues.
• If Reliability is the top priority → Buy a new OEM or reputable remanufactured GPCM.

Warranty tradeoff: Used parts typically have a 30-90 day warranty. New aftermarket parts offer a 1-year warranty. New OEM parts carry the manufacturer's warranty.

Worst-case if a used part fails: $150-$300 if a used GPCM fails shortly after installation, requiring repeat labor and another part.

What Happens If You Wait — Timeline

1. 0-1 month: Check Engine Light on. In cool weather (<50°F), engine cranks for 1-2 extra seconds and idles slightly rough for 15-30 seconds. (MPG impact: 0-2%% · Added cost: $0)
2. 1-4 months: Hard starting becomes consistent below 60°F. Noticeable white smoke and a raw diesel smell from the exhaust for the first minute. (MPG impact: 3-5%% · Added cost: $25-$75 in wasted fuel.)
3. 4-8 months: Engine requires extended cranking in warm weather. Misfire causes hesitation. Increased soot clogs the DPF, triggering frequent regenerations. (MPG impact: 5-10%% · Added cost: $100-$300 in wasted fuel and early DPF stress.)
4. 8+ months: Risk of being stranded with a no-start. The DPF permanently clogs, triggering limp mode and requiring professional cleaning or replacement. (MPG impact: 10-20%% · Added cost: $600-$5000+ for DPF cleaning or replacement.)

Cost of Not Fixing It

• Immediate: Hard starting in cold weather, rough idle, and white smoke on startup. Stranded with a no-start is possible. (Added cost: Negligible, but high inconvenience.)
• 1-6 months: Incomplete combustion in cylinder 3 increases soot production. This overwhelms the Diesel Particulate Filter (DPF), causing frequent regenerations and reducing fuel economy. (Added cost: $50-$200 in lost fuel efficiency.)
• 6+ months: The DPF permanently clogs with soot because the faulty glow plug prevents proper regeneration temperatures. The DPF requires professional cleaning or full replacement. (Added cost: $600-$1500 for professional cleaning, or $2000-$5000+ for DPF replacement.)

Diagnosis Steps

1. Verify the Code
   Use an OBD-II scanner to confirm P0673 is active. Document other codes, as they point to broader issues (e.g., P0670 for a module fault, or P0671/P0672 pointing to a relay). Clear the codes and see if P0673 returns after a cold start.
   Tools: OBD-II Scanner (Beginner)
2. Test Glow Plug Resistance
   Disconnect the electrical connector from the #3 glow plug. Set a multimeter to Ohms (Ω). Place one probe on the glow plug's terminal and the other on the engine block (ground). A good glow plug reads between 0.6 and 2.0 ohms. A reading of 'OL' (Over Limit) or resistance over 6 ohms confirms an open circuit and a dead glow plug.
   Tools: Multimeter (Intermediate)
3. Visual Inspection of Cylinder 3 Circuit
   Locate the cylinder 3 glow plug. Inspect the wire and connector for burning, melting, corrosion, or looseness. Check the bus bar or harness connecting the plugs for visible damage.
   Tools: Flashlight, Mirror (Beginner)
4. Check for Voltage at the Connector
   Have a helper turn the ignition to 'ON' (do not start). Set a multimeter to DC Volts. Connect the black lead to engine ground and probe the glow plug connector's terminal with the red lead. You should see battery voltage (10.5V - 12.5V) for a few seconds as the GPCM cycles the plug. No voltage points to a wiring, GPCM, or relay problem.
   Tools: Multimeter, Helper (Intermediate)
5. Inspect Fuses and Relays
   Consult the fuse box diagram to locate glow plug system fuses or relays. Visually inspect the main GPCM fuse for breaks. Swap the glow plug relay with a known good one (like the horn relay) to test for failure.
   Tools: Owner's Manual, Fuse Puller (Beginner)
6. Test the Glow Plug Control Module (GPCM) Output
   If the plug, wiring, and fuses are good, suspect the GPCM. Back-probe the output pin for cylinder 3 at the GPCM connector while activating the glow plugs. If you have battery voltage entering the module but no voltage exiting on the cylinder 3 circuit, the module failed.
   Tools: Multimeter, Vehicle-Specific Wiring Diagram (Advanced)
7. Pro Tip: Perform a Voltage Drop Test
   Confirm ground circuit integrity. Set the multimeter to DC Volts. Connect the red lead to the engine block and the black lead to the negative battery terminal. Have a helper activate the glow plugs. The reading must be less than 0.2 volts. Higher readings indicate a poor engine-to-battery ground.
   Tools: Multimeter, Helper (Advanced)
8. Pro Tip: Test Circuit Current with an Amp Clamp
   For intermittent issues, place an inductive amp clamp around the cylinder 3 power wire. During activation, current draw should hit 10-20 amps, then taper off. Zero amps confirms an open circuit. Extremely high readings suggest a short.
   Tools: Inductive Amp Clamp, Multimeter (Advanced)
9. Advanced: Analyze Scan Tool Live Data
   Monitor live data PIDs like 'Glow Plug Lamp Command' and 'Glow Plug #3 Circuit Status'. The desired state is 'ON' or 'OK' during pre-heat. A 'Fault' or 'Open' status points directly to the circuit. Command a GPCM self-test to check output drivers.
   Tools: Advanced Bi-Directional OBD-II Scanner (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: Below 40°F (5°C) (Engine is cold, prior to or during startup.)
• RPM: 0 or < 200 (Key-On, Engine-Off (KOEO) or during initial cranking.)
• Time Since Engine Start: 0-10 seconds (The fault is detected during the pre-heat cycle immediately after turning the key.)
• Battery Voltage: 10.5V - 12.5V (System voltage during the high-current draw of the glow plug cycle.)

Related Codes

• P0670 — Indicates a general fault in the Glow Plug Control Module circuit. If seen alongside P0673, the GPCM, its power supply, or ground is the primary suspect, not an individual plug.
• P0671, P0672, P0674, P0675, etc. — Identical to P0673 but for different cylinders. Multiple codes strongly suggest a systemic problem affecting all plugs, like the GPCM, main fuse, or relay.
• P0683 — Indicates a communication problem between the GPCM and PCM. If paired with P0673, the GPCM is failing, has bad power/ground, or cannot communicate its status.
• P037D, P037E, P037F — Related 'Glow Plug Sense Circuit' codes indicating specific low or high voltage readings, pointing directly to wiring shorts or resistance problems.

Climate & Environmental Factors

• Cold Climate: Glow plug failures are most noticeable in cold weather. The system is critical for starting a diesel engine when ambient temperatures are low. Vehicles in colder regions experience more frequent glow plug cycles, leading to shorter lifespans.
• Short-Trip Driving: Vehicles used for short trips experience more start-stop cycles, causing frequent glow plug use. This accelerates wear and leads to premature failure compared to highway driving.
• Humidity and Moisture: High humidity or road salt accelerates corrosion on glow plug wiring, connectors, and the GPCM. Corrosion increases electrical resistance, triggering circuit codes like P0673.
• Altitude: At higher altitudes, less dense air results in lower compression pressures and temperatures. The engine relies heavily on the glow plug system to achieve ignition temperatures, making marginal glow plugs fail noticeably.

How to Talk to a Mechanic About This Code

Say this: "I have a P0673 code for the cylinder 3 glow plug circuit. Please test the resistance of the glow plug and check for voltage at the connector before recommending a new control module."

This directs the mechanic to follow a logical diagnostic path, preventing them from quoting an expensive GPCM before verifying the simple things.

Avoid saying:

• 'My truck won't start right, can you fix it?'
• 'My check engine light is on, I think it's a glow plug.' (Too vague, invites upselling)
• 'Just replace the cylinder 3 glow plug.' (Don't authorize a repair without a diagnosis; it could be wiring or the module)

Questions to ask before authorizing the repair:

• What was the ohm reading on the cylinder 3 glow plug?
• Did you see battery voltage at the glow plug connector when the key was cycled?
• If recommending a new GPCM, did you confirm it has power and ground but no output on the cylinder 3 wire?
• What is the warranty on the parts and labor for this repair?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended for warranty work or if your vehicle has a known, complex quirk related to this code.
  Best for: Vehicles under powertrain or emissions warranty., Complex manufacturer-specific issues (e.g., VW Pressure-Sensing Glow Plugs, Duramax GPCM Special Coverage)., Repairs where the risk of breaking a glow plug is high and you want the dealer to assume liability.
  Downsides: Highest labor rates, typically 1.5-2x more than an independent shop., May recommend replacing an entire set of glow plugs or a harness when only one component failed. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit, especially a well-regarded independent diesel specialist. They provide better value and real-world experience.
  Best for: Out-of-warranty vehicles where cost is a primary concern., Shops specializing in diesel engines (e.g., Powerstroke, Duramax, Cummins)., Straightforward glow plug or GPCM replacement on common truck models.
  Downsides: Quality and experience with diesel systems vary widely. Vet shops carefully through reviews. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID. The risk of misdiagnosis and lack of specialized tools (like for a broken glow plug) is too high.
  Best for: Simple services like oil changes or tire rotations.
  Downsides: Technician skill with complex diesel diagnostics is limited., High pressure to upsell services; may misdiagnose the issue. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost for the P0673 fault exceeds 40-50% of your diesel vehicle's private-party value, pause and evaluate your options.

• Car worth $8000, fix is $450: Fix it. A standard repair including a full set of glow plugs is well below the threshold and is good preventive maintenance.
• Car worth $6000, fix is $2200: Borderline. This involves a worst-case scenario like a broken glow plug extraction plus a new GPCM. Get a second opinion.
• Car worth $3500, fix is $1800: Walk away. The repair cost is over 50% of the vehicle's value. It is not economically sound to proceed.

What Scan Tool You Need for This Code

Minimum: A code reader that displays live data PIDs for the glow plug system. A basic $20 reader is not enough.

To properly diagnose P0673, you need to see what the control module sees. A basic reader won't show live 'Glow Plug Lamp Status' or confirm voltage commands.

Budget: BlueDriver Pro Scan Tool (~$100) — Connects to your smartphone to read P0673, view freeze-frame data, and monitor live data PIDs like 'Glow Plug Lamp Status', crucial for initial diagnosis.

Mid-range: FOXWELL NT510 Elite or THINKCAR Thinkscan 689BT (~$150) — Offers full system diagnostics and bi-directional control. Allows you to command the GPCM to run a self-test or manually cycle the glow plugs, providing definitive proof of module function.

Professional: Autel MaxiCOM MK808/MK900 or XTOOL D7 (~$450-800) — Provides full OEM-level bidirectional control, live data graphing, and access to manufacturer-specific tests. Performs advanced functions like glow plug relearn procedures.

Rent vs buy: Auto parts stores rent basic code readers for free, but they lack live data. Buying a scanner in the $100-$150 range pays for itself by avoiding one misdiagnosis.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear the P0673 fault code.
2. Perform a cold start (after the vehicle sits for several hours) to allow the GPCM to verify the repair.
3. Drive the vehicle for at least one full warm-up cycle to reset readiness monitors.

Drive cycle (~20 minutes): Cold start the engine and idle for 2-3 minutes. Drive in mixed city/highway conditions for 15-20 minutes, including steady-state cruising. Allow the vehicle to cool completely to ambient temperature.

Readiness monitors affected: Comprehensive Component Monitor, Misfire Monitor

Watch out for:

• Disconnecting the battery clears the code but resets all readiness monitors, causing an automatic emissions test failure.
• The code returns on the next cold start if the underlying electrical fault remains.

Will This Fail Emissions / State Inspection?

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

• California: An active Check Engine Light causes an automatic smog check failure. All readiness monitors must be 'Ready', so you cannot simply clear the code before inspection.
• New York: A Check Engine Light is an automatic failure. After repair, the vehicle must complete a drive cycle so the OBD-II system is 'Ready'.
• Texas: In emissions-testing counties, an active P0673 code is an automatic failure. Clearing the code right before the test results in a 'Not Ready' status, which also fails.

Most Commonly Affected Vehicles

• Ford F-250/F-350 Super Duty (Powerstroke) (2008-2016) — Common for both glow plug and GPCM failures. On the 6.7L, cylinder 3 is on the passenger side. Early 2011 models (built before 3/29/2011) had exhaust valve seats fail, physically damaging the glow plug.
• Chevrolet / GMC Silverado 2500HD / Sierra 2500HD (Duramax) (2004-2010) — The GPCM is a frequent failure point on LB7, LLY, and LBZ engines. Accessing glow plugs requires removing the fender liner. Check for loose battery connections per TSB #PIP3586G.
• Volkswagen Jetta / Golf / Passat (TDI) (2009-2015) — On CJAA and CBEA engines, cylinder 3 often uses an expensive Pressure Sensing Glow Plug (PSGP). Replacing it with a standard plug will not resolve the issue.
• Dodge / Ram 2500 / 3500 (Cummins) (2007-2018) — While most Cummins engines use an intake air heater grid, certain configurations equipped with individual glow plugs are susceptible to these circuit faults.
• Mercedes-Benz Sprinter / E320 / ML320 (CDI) (2007-2018) — The OM642 and other CDI engines frequently log glow plug faults. The glow plug control module is a common failure point when multiple codes appear.
• BMW 335d, X5 xDrive35d (2009-2013) — On the M57 engine, this code is often due to a failed glow plug or GPCM. Significant carbon buildup makes removal difficult, increasing breakage risk.
• Jeep Grand Cherokee (EcoDiesel) (2014-2018) — The 3.0L VM Motori EcoDiesel logs this code. Diagnosis follows checking the plug, wiring, and the module located in the engine valley.
• Toyota Hilux / Innova (1GD/2GD Engine) (2020-2023) — The glow plug tip breaks off inside the cylinder head, creating an open circuit and requiring careful extraction to prevent engine damage.

Manufacturer-Specific Notes

• Ford: On 6.7L Powerstroke engines built before March 29, 2011, defective exhaust valve seats fail and contact the glow plug, destroying it and triggering this code.
• Volkswagen/Audi: Modern TDI engines use a Pressure Sensing Glow Plug (PSGP) in one cylinder (often #3). These are physically different and expensive. Using a standard part will not fix P0673.
• GM (Duramax): The GPCM is a common failure point. TSB #PIP3586G advises checking for loose battery feed connections. GM issued Special Coverage Adjustment #15385 for 2010-2012 Duramax engines, extending glow plug warranties to 10 years/120,000 miles.
• Mercedes-Benz: On CDI engines, the glow plug relay/module is the most common failure point. Replace the module if you have glow plug codes and the plugs test good.

Real Owner Stories

2014 VW Jetta TDI at 85,000 miles - The Misdiagnosis

Check Engine Light came on with P0673. Car had a slightly slower crank in the morning but otherwise ran fine.

What they tried:

1. Replaced the cylinder 3 glow plug with a standard plug. The code returned immediately.
2. Tested the new plug, assumed the GPCM was bad, and replaced it. The code still returned.
3. Took it to a specialist who identified cylinder 3 required a Pressure Sensing Glow Plug (PSGP).

Outcome: Replacing the plug with the correct OEM PSGP (part # 03L-905-061-G) for $150 cleared the code and resolved the slow crank.

Lesson: On modern TDIs, one cylinder uses a special Pressure Sensing Glow Plug. Verify the exact part number, as a standard plug will not work.

2006 GMC Sierra 2500HD (LLY Duramax) at 160,000 miles - The Easy Fix

Truck became hard to start below 40°F, blowing white smoke and running rough. Code P0673 appeared.

What they tried:

1. Tested the cylinder 3 glow plug with a multimeter. The resistance test showed 'OL' (over limit), indicating a dead plug.
2. All other plugs tested within the normal 0.6-2.0 ohm range.

Outcome: Replaced only the failed glow plug in cylinder 3 (ACDelco 9G) for under $30. The code cleared and the truck started perfectly.

Lesson: A single-cylinder glow plug code is most often just a failed glow plug. A 5-minute resistance test confirms this and saves money.

2012 Ford F-350 (6.7L Powerstroke) at 125,000 miles - The Broken Plug

P0673 code appeared. Owner decided to replace all 8 glow plugs. The cylinder 3 glow plug snapped off in the cylinder head.

What they tried:

1. Attempted removal on a cold engine without penetrating oil.
2. Tried using a standard screw extractor, which failed and damaged the broken piece.

Outcome: The $200 DIY job turned into a $1,200 repair bill. A mechanic used a specialized extraction tool kit to drill out the broken plug without removing the cylinder head.

Lesson: Glow plug breakage is a major risk. Perform the job on a warm engine, soak plugs in penetrating oil, and use slow, even turning force.

How to Prevent This Code From Triggering

• Use high-quality diesel fuel and a reputable fuel additive (Every fill-up) — Quality fuel with detergents reduces carbon deposit formation on glow plug tips, preventing insulation and removal difficulties.
• Replace all glow plugs proactively (Every 80,000-100,000 miles) — Glow plugs are wear items. Replacing them as a set prevents no-start conditions and avoids repeated labor costs.
• Avoid excessive idling and short trips (Daily habit) — Short trips prevent the engine from reaching operating temperature, accelerating carbon buildup on glow plugs.
• Clean glow plug holes during replacement (During glow plug replacement) — Using a reamer or wire brush to clean carbon deposits ensures the new plug seats correctly and has proper heat transfer, preventing it from seizing.
• Maintain the vehicle's electrical system (Annually) — Clean battery terminals and ground connections. Poor grounds cause low voltage to the GPCM, affecting performance and damaging the module.

Frequently Asked Questions

What is the difference between a glow plug and a spark plug?

A spark plug creates a high-voltage spark to ignite gasoline. A glow plug is a heating element that warms a diesel engine's combustion chamber, allowing fuel to auto-ignite under high compression.

Should I replace just one bad glow plug or all of them?

Glow plugs wear at a similar rate. While replacing only the failed plug clears the code, replacing all of them at once prevents future failures and saves on repeated labor costs.

What is the biggest mistake when diagnosing P0673?

The most common mistake is replacing the expensive Glow Plug Control Module without testing the glow plug and its dedicated wire first. A single cylinder fault like P0673 is almost always caused by the plug itself.

Can a glow plug get stuck or break during removal?

Yes, carbon buildup causes glow plugs to seize and break in the cylinder head, requiring expensive extraction. Always attempt removal on a warm engine, apply penetrating oil, and use slow, steady force.

What is the torque spec for a glow plug?

Glow plug torque specs are extremely low, ranging from 13 lb-ft on older engines to 89 in-lbs on newer ones. Overtightening snaps the plug. Always use a calibrated torque wrench and your vehicle's exact specification.

How much does a P0673 diagnosis cost?

Most auto repair shops charge a standard diagnostic fee covering one hour of labor, typically $120 to $180. This fee is often applied as a credit toward the total repair cost.

Can I test a glow plug without removing it?

Yes. You can perform a resistance test with a multimeter by simply disconnecting the electrical connector. You can also perform a current draw test with an amp clamp around the wire.

Key Takeaways

• P0673 indicates an electrical failure in the cylinder 3 glow plug circuit, causing hard starts and rough idling in temperatures below 60°F.
• Test the cylinder 3 glow plug's resistance with a multimeter; a reading above 2.0 ohms confirms the plug is dead and requires replacement.
• Replace all engine glow plugs simultaneously (typically $300-$700 parts and labor) if your vehicle has over 80,000 miles to prevent cascading failures.
• Soak the old glow plug in penetrating oil and remove it from a warm engine to prevent it from snapping off, which turns a $50 DIY job into a $1,200+ extraction.
• Never replace the $150-$300 Glow Plug Control Module (GPCM) without first verifying the cylinder 3 wire has continuity and the plug itself is faulty.