P0198 on 2019-2024 Chevy Silverado 1500 3.0L Duramax: Engine Oil Temp Sensor Fixes

What's Unique About the 2019-2024 Chevrolet Silverado 1500

The 3.0L Duramax (both LM2 and LZ0 versions) has a complex thermal management system. A very common failure on this engine is the Engine Coolant Control Valve, which triggers a P1098 code and is an expensive repair, though often covered by a GM Special Coverage program (N252508341 for LM2, N252508340 for LZ0). Some owners with a P0198 code have reported being sold this costly coolant valve repair, suggesting it's a frequent misdiagnosis. Additionally, GM documentation confirms this engine uses two separate Engine Oil Temperature sensors, so a proper diagnosis is key to identifying the correct one.

Symptoms You May Notice

• Check Engine Light is on
• Incorrect reading on the oil temperature gauge (if equipped)
• Engine cooling fans may run continuously at high speed
• In some cases, reduced engine power or "limp mode"

Most Likely Causes

1. Failed Engine Oil Temperature (EOT) Sensor 🔴 High Probability Sensors can fail over time due to heat cycles and exposure to engine oil and contaminants. It is a simple thermistor that degrades.
   How to confirm: After checking the wiring, test the sensor's internal resistance with a multimeter while applying heat; the resistance should change smoothly. Alternatively, swap the sensor with a new one, as it is an inexpensive part. A typical thermistor sensor will have high resistance when cold (e.g., 2000-3000 Ohms at 20°C/68°F) and low resistance when hot (e.g., 200-300 Ohms at 90°C/194°F).
   Typical fix: Replace the faulty Engine Oil Temperature sensor. On the 3.0L Duramax, it is located on the driver's side of the engine, just above the oil filter housing.
   Est. part cost: $20-$50
2. Damaged Wiring or Connector 🟡 Medium Probability GM issued TSB 23-NA-102 for 2022-2024 models, noting that the engine wiring harness can chafe against brackets (like the alternator bracket), causing various electrical faults. An open circuit or short-to-voltage in the EOT sensor harness will trigger P0198. The TSB specifically shows images of the harness rubbing on the alternator bracket due to mis-installed retainer pins.
   How to confirm: Visually inspect the wiring harness leading to the EOT sensor for any signs of chafing, melting, or corrosion. Check for a stable 5-volt reference signal and a good ground at the sensor connector with the key on. TSB 23-NA-102 provides specific locations to check for harness damage near the alternator.
   Typical fix: Repair the damaged section of the wiring harness using approved SI procedures and secure it away from sharp edges or heat sources. Clean or replace the connector if it is corroded. Protective conduit or hose can be added to prevent future chafing.
   Est. part cost: $5-$25 for repair materials
3. Faulty Engine Control Module (ECM) ⚪ Low Probability
   How to confirm: This is diagnosed by exclusion. If the sensor and its entire circuit (wiring, connectors, power, ground) test perfectly, the ECM's internal driver for the sensor may be at fault.
   Typical fix: Replace and reprogram the Engine Control Module. This must be done by a dealership or a qualified shop with programming capabilities.
   Est. part cost: $600-$1200

Diagnosis Steps

1. Read the code with an OBD-II scanner and check for any other stored codes.
2. Use the scanner's live data function to observe the Engine Oil Temperature reading. A reading of -40°F or an extremely high, unchanging value points to a circuit fault. A high default value like 1832°F can also indicate an open circuit.
3. Locate the Engine Oil Temperature sensor. On the 3.0L Duramax, it is on the driver's side of the engine block, positioned just above the oil filter housing.
4. Inspect the sensor's electrical connector and wiring harness. Look for loose connections, corrosion, or physical damage. Pay close attention to the wiring harness routing near the alternator bracket, as detailed in TSB 23-NA-102, checking for chafing or pinching.
5. With the key on and engine off, disconnect the sensor and use a multimeter to check for a 5-volt reference signal on one wire and a good ground on another.
6. If the wiring and connector are confirmed to be good, the sensor itself is the most likely culprit.
7. Replace the Engine Oil Temperature sensor. Clear the codes and perform a test drive to ensure the code does not return.

Parts You'll Likely Need

• Engine Oil Temperature Sensor (OEM #55494665) — This sensor is the most common failure point for a P0198 code. It is a simple thermistor that can degrade over time.
  Trusted brands: GM Genuine Parts, ACDelco
  OEM price range: $19-$40
  Aftermarket price range: $15-$35

Related Codes That Often Appear With This One

• P0197 — This code means 'Engine Oil Temperature Sensor Circuit Low,' and seeing it along with P0198 can indicate an intermittent wiring problem or a failing sensor.
• P1098 — This code for 'Coolant Control Valve Performance' is extremely common on this engine and shares the symptom of the cooling fan running constantly. While it's a separate issue, its prevalence leads to misdiagnosis. A dealer may incorrectly try to fix P0198 by addressing P1098.

Technical Service Bulletins (TSBs) & Recalls

• 23-NA-102: Addresses potential for engine wiring harness to contact the alternator bracket or other components, causing chafing and various DTCs on 2022-2024 models. While P0198 is not explicitly named, this TSB describes a likely root cause for the fault.
• N252508341 / N252508340: These are Special Coverage Programs, not TSBs, that extend the warranty on the Engine Coolant Control Valve to 15 years/150,000 miles for LM2 and some LZ0 engines, respectively. This is relevant due to the common misdiagnosis between P0198 and P1098.

Platform-Specific Known Issues

• Wiring Harness Chafing: TSB 23-NA-102 highlights a known issue on 2022-2024 models where the engine wiring harness can rub against the alternator bracket or other components, leading to various electrical faults. This is a highly probable cause for a P0198 circuit code. The bulletin shows specific photos of the harness chafing due to mis-installed retainer pins, causing it to rest on the alternator.
• Dual Oil Temp Sensors: GM service information bulletin 19-NA-180 indicates the LM2 3.0L Duramax is equipped with two separate engine oil temperature sensors. A professional scan tool may be needed to determine which sensor circuit is setting the fault.
• Misdiagnosis with Coolant Control Valve: The P1098 code for the coolant control valve is a very frequent, separate issue on these engines. A Reddit user with a P0198 code was quoted a $4,000 repair for the coolant valve system, highlighting the potential for expensive misdiagnosis.

Mechanic-Grade Diagnostic Values

• EOT Sensor Reference Voltage — expected: ~5.0 Volts. Failure: Voltage significantly lower or higher than 5.0V indicates a wiring or ECM issue.
• EOT Sensor Resistance (Cold Engine) — expected: 2000 - 3000 Ω (at ~20°C / 68°F). Failure: An open circuit (infinite resistance) or a short (near zero resistance) indicates a failed sensor.
• EOT Sensor Resistance (Warm Engine) — expected: 200 - 300 Ω (at ~90°C / 194°F). Failure: Resistance does not decrease as the engine warms up, or the reading is erratic.
• Scan Tool Live Data (Open Circuit) — expected: Normal operating temperature (e.g., 180-240°F). Failure: A default high reading, such as 1832°F, or an extremely low reading like -40°F.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Data Display for Engine Control Module — To monitor live data from both Engine Oil Temperature Sensor 1 and Sensor 2 to determine which circuit is faulting, as this engine has two EOT sensors.
• GDS2 (GM Global Diagnostic System 2): DTC Information / Freeze Frame — To view the specific conditions (engine speed, temperature, etc.) under which the P0198 code was set, which can help differentiate an intermittent wiring fault from a hard sensor failure.

Wiring & Ground Locations

• Engine Oil Temperature Sensor Connector — On the driver's side of the engine block, directly above the oil filter housing.. This is the primary connection point to test for 5V reference, ground, and signal integrity. Corrosion or damage here is a common cause of circuit faults.
• Engine Harness Ground (Typical) — Typically bolted to the cylinder head or engine block near the main harness breakout. Specific G-number locations require a service manual.. A poor ground connection for the EOT sensor circuit can cause a floating voltage, leading to a high circuit code like P0198.
• Harness Chafing Point (per TSB 23-NA-102) — Engine wiring harness near the alternator bracket.. A known issue where mis-routed harness retainers allow the harness to rub on the alternator bracket, potentially causing an open or short in the EOT sensor circuit wires.

Real Owner Repair Stories

• Reddit user 'dadtothree' (2021 GMC 1500 3.0L Duramax, 50k miles) — Check Engine Light with code P0198.
  ❌ Tried (didn't work) Initial diagnosis was unclear.
  ✅ What actually fixed it The dealership diagnosed a bad auxiliary coolant pump and coolant valve, a repair costing the owner approximately $3,100 - $4,000. This highlights the common and expensive misdiagnosis of P0198 as a P1098-related coolant system failure.

OEM Part Supersession History

• ACDelco GM Original Equipment (OE) → GM Genuine Parts 55494665 — Branding change. GM is consolidating its OEM parts under the 'GM Genuine Parts' name.
  Heads up: Parts are identical and fully compatible.

Model Year Variations Within This Range

• 2020-2022 (LM2 Engine): GM Service Bulletin 19-NA-180 explicitly confirms the LM2 engine uses two separate Engine Oil Temperature sensors. Diagnosis may require a scan tool capable of differentiating between Sensor 1 and Sensor 2 data.
• 2022-2024 (Primarily LZ0 Engine): These model years are specifically called out in TSB 23-NA-102 regarding the potential for the engine wiring harness to chafe against the alternator bracket. While possible on earlier models, it is a documented pattern on these later years.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Engine Coolant Control Valve Failure (P1098) 🔴 High — Very common across all model years with the LM2/LZ0 engine. Symptoms include fans running at high speed after shutdown and reduced power warnings. (Ref: Special Coverage N252508341 (LM2) & N252508340 (LZ0) extend warranty to 15 years/150,000 miles.)
• Rear-Mounted Oil Pump Drive Belt Replacement 🟠 Medium — This is a scheduled maintenance item, not a common failure. However, it is a very expensive and labor-intensive job (14+ hours) requiring transmission removal. The service interval is 150,000 miles for LM2 and 200,000 miles for LZ0.
• Crank-No-Start Condition 🟠 Medium — Reported on a significant number of early LM2 engines. The engine will crank for an extended period without starting, but may start on a second attempt. (Ref: Dealers have performed ECM software updates to address this, which typically lengthens the default cranking time.)
• DEF System and Emissions Sensor Failures 🟠 Medium — Failures of DEF sensors and other emissions components are a common complaint, leading to 'Service Emission System' warnings and potential 'limp mode'. (Ref: TSB #21-NA-07 addresses DEF sensor issues on some models.)
• Early LM2 Timing Chain Issues 🔴 High — Some early production 2020-2021 LM2 engines reportedly had issues with timing chain stretch and guide failure, which could lead to catastrophic engine damage.
• LZ0 Crankshaft End-Play / Thrust Bearing Failure 🔴 High — A manufacturing defect in some 2023-2025 LZ0 engines can cause excessive crankshaft movement ('end-play'), leading to noise, oil pressure codes (P06DD), and potential engine failure at very low mileage. (Ref: TSB 25-NA-307 provides diagnostic procedures for dealers to measure crankshaft end play.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this repair, a used part is generally not recommended. The primary failure part, the EOT sensor, is inexpensive to buy new. A used wiring harness could be a cost-effective option ONLY if a large section is damaged and a new harness is prohibitively expensive, but it must be inspected meticulously.

Donor-vehicle mileage cap: roughly under 75000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a wiring harness: Check the entire length for signs of chafing, brittleness, or previous repairs.
• For connectors: Ensure locking tabs are intact and not brittle. Look for any signs of corrosion or pushed-out pins.
• Verify the donor vehicle was not from a region with heavy road salt use, which accelerates corrosion.

OEM-only on this vehicle (don't cheap out):

• Engine Oil Temperature Sensor: Given the low cost and critical function, using an OEM (GM Genuine / ACDelco) sensor is highly recommended to ensure accurate readings and longevity.

Brands owners have reported issues with on this vehicle:

• Unnamed, no-brand sensors from online marketplaces should be avoided, as their thermistor accuracy and durability are often questionable.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P1098 — A very frequent code for the coolant control valve failure on this platform; often confused with P0198 due to overlapping symptoms like high-speed cooling fans.
• P0197 — The low-voltage counterpart to P0198, indicating the Engine Oil Temperature sensor circuit is below the expected range rather than high/open.

Frequently Asked Questions