P0202 on 2009-2014 Buick LaCrosse: Injector Circuit Malfunction Causes and Fixes

What's Unique About the 2009-2014 Buick LACROSSE

For this generation of Buick LaCrosse and other GM vehicles with the 3.0L and 3.6L V6 engines, a key issue is the fuel injector wiring harness. A GM Technical Service Bulletin (TSB PIP4924D) specifically advises technicians to inspect the harness for damage where it might rub against the intake plenum, valve cover bolts, fuel lines, and the side of the cylinder head. This suggests that a wiring fault is a more common cause on these vehicles than on others where the injector itself might be the primary point of failure. A newer TSB (PIE0802) from 2024 also points to GM actively investigating harness contact with the Cam Shaft Housing Cover Insulator as a root cause for P0202.

Diagnostic Flowchart

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

Generation note: The specified range of 2009-2014 includes the last year of the first-generation LaCrosse (2009, W-body) and the second generation (2010-2014, Epsilon II platform). However, the TSBs covering this issue apply to both generations and the engines (like the 3.6L V6) used across them, so the causes and diagnostic steps are broadly similar. A critical change occurred in 2012 when the 3.6L V6 was updated from the LLT to the LFX version, which uses different fuel injectors and ECM.

Symptoms You May Notice

• Check Engine Light is on
• Engine misfire or running rough, especially at idle
• Hesitation or loss of power during acceleration
• Poor fuel economy
• Engine may feel like it's stumbling or shaking

Most Likely Causes

1. Damaged Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness A GM TSB (#PIP4924D) specifically points to the injector wiring harness chafing against engine components. Common rub-through spots are against the intake plenum, at valve cover bolts, against a fuel line, or on the side of the cylinder head under the plenum. Heat and vibration can cause the loom to wear through, exposing wires which then short to ground or break.
   How to confirm: Visually inspect the entire wiring harness leading to the cylinder 2 fuel injector. Pay close attention to the specific points mentioned in TSB PIP4924D. Look for rubbed-through insulation, broken wires, or signs of heat damage. A YouTuber found a mouse had chewed through an injector wire on a similar GM V6 engine.
   Typical fix: Repair the damaged section of wire using solder and heat shrink, or replace the entire fuel injector wiring harness pigtail if the damage is near the connector or extensive.
   Est. part cost: $5-$20 for wire repair, $75-$150 for a new harness pigtail or section.
2. Faulty Fuel Injector 🔴 High Probability → Shop Fuel Injector The 3.6L V6 uses direct injection (GDI) injectors which operate under high pressure and can fail internally over time from heat cycles and wear. The internal coil can burn out or develop high resistance, causing an electrical fault.
   How to confirm: Swap the cylinder 2 fuel injector with one from another cylinder (e.g., cylinder 4). Clear the codes and run the engine. If the code changes to P0204, the injector is faulty. You can also test the injector's internal resistance with a multimeter. For 2009-2011 LLT engines, expect ~12 Ohms. For 2012-2014 LFX engines, expect 1.2-1.8 Ohms. A reading significantly outside this range indicates a bad injector. Note: Accessing the injectors requires removing the upper intake manifold.
   Typical fix: Replace the faulty fuel injector. It is highly recommended to replace all Teflon seals and retaining clips at the same time. Since the intake manifold must be removed, it is also mandatory to replace the intake manifold gaskets.
   Est. part cost: $95-$130 for a single OEM (ACDelco) injector.
3. Corroded or Loose Connector 🟡 Medium Probability The connector at the fuel injector or the PCM can become loose or contaminated with moisture and dirt over time, leading to a poor connection. The locking tab can become brittle and break.
   How to confirm: Disconnect the electrical connector at the cylinder 2 injector and inspect the pins for corrosion, dirt, or damage. Ensure it clicks securely back into place. Wiggle the connector with the engine running to see if it induces a misfire.
   Typical fix: Clean the connector pins with electrical contact cleaner. If the connector or its pins are damaged, the connector pigtail will need to be replaced.
   Est. part cost: $10-$25 for a new pigtail connector.

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is the least likely cause, but it is a known failure mode on this platform. If the wiring and injector test good, the internal driver circuit in the PCM for the injector can fail. All other possibilities must be exhausted before condemning the PCM. A user on the ScannerDanner forum with a 2011 LaCrosse confirmed a bad ECM was the cause for multiple injector codes after extensive testing. A YouTube video shows a similar diagnosis pointing towards a faulty ECU on a 2011 LaCrosse with P0202 and P0204.

Diagnosis Steps

1. Scan the vehicle for any other stored trouble codes to get a full picture of the issue.
2. Visually inspect the wiring harness for cylinder 2's fuel injector. Look for any signs of chafing, melting, or corrosion, especially in the areas mentioned in TSB PIP4924D (near the intake, valve covers, and fuel lines).
3. Inspect the electrical connector on the injector. Check for loose pins, corrosion, or damage. Ensure the locking tab is secure.
4. Use a noid light to test for a signal. Disconnect the injector and plug in the noid light. Crank the engine; the light should flash, indicating the PCM is sending a signal. If it doesn't flash, the problem is in the wiring or PCM.
5. If the noid light flashes, test the fuel injector's resistance. Unplug the injector and use a multimeter set to ohms to measure the resistance between its two electrical pins. Compare this to the specification (11.8-12.6 Ohms for 2009-2011 LLT, 1.2-1.8 Ohms for 2012-2014 LFX). A reading of 'OL' (open) or a value significantly different from other injectors indicates a bad injector.
6. To definitively confirm a bad injector, perform an injector swap test. This requires removing the upper intake manifold. Move the cylinder 2 injector to another cylinder (like cylinder 4). Reassemble with new gaskets, clear the codes, and drive the vehicle. If the code returns as P0204, the injector is confirmed to be faulty. If P0202 returns, the issue is in the wiring or PCM.
7. If the injector and signal are good, perform a continuity test on the wiring between the injector connector and the PCM connector to find any breaks or shorts in the wire.

Parts You'll Likely Need

• Fuel Injector (OEM #12634126) — This is a common failure point that directly causes the P0202 code when its internal coil fails. This is a GDI injector. Note that this part number is for the LLT engine (2009-2011). The LFX engine (2012-2014) uses a different injector.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $95-$130
  Aftermarket price range: $50-$90
• Upper Intake Manifold Gasket Set (OEM #12609260 (example, verify by VIN)) — Required for reassembly. The upper intake manifold must be removed to access the fuel injectors on the 3.6L V6 engine. These gaskets are single-use and must be replaced to prevent vacuum leaks.
  Trusted brands: Fel-Pro, ACDelco
  OEM price range: $30-$50
  Aftermarket price range: $15-$30
• Fuel Injector Connector Pigtail (OEM #PT2183 (ACDelco)) — If the connector itself is damaged, corroded, or the locking tab is broken, it must be replaced to ensure a solid electrical connection.
  Trusted brands: ACDelco, Dorman
  OEM price range: $20-$35
  Aftermarket price range: $10-$20

Related Codes That Often Appear With This One

• P0302 — P0302 means "Cylinder 2 Misfire Detected." Since a P0202 fault prevents the injector from delivering fuel, it will almost always cause a misfire in that cylinder.
• P0201, P0203, P0204, P0205, P0206 — If multiple injector codes are present, it strongly suggests a wiring harness issue common to all affected injectors (like a damaged section of the main harness) or a problem with the PCM itself.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: "SES Light And Misfire With Injector Codes" - Advises inspecting the fuel injector wiring harness for chafing against the intake plenum, valve cover bolts, fuel line, and cylinder head.
• PIE0802: "Engineering Information - Check Engine Lamp Il

Platform-Specific Known Issues

• A known issue documented in GM TSB PIP4924D is the fuel injector wiring harness rubbing through against various engine components, causing an open or short circuit. This is a primary diagnostic starting point for this code on this vehicle.
• A recent GM Engineering Information bulletin (PIE0802, Sept 2024) has been issued specifically for DTC P0202, requesting technicians to inspect for contact between the wiring harness and the Cam Shaft Housing Cover Insulator, indicating this is an area of active investigation by GM.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (2009-2011 3.6L LLT Engine) — expected: 11.8 - 12.6 Ohms. Failure: A reading significantly outside this range, or OL (Open Line), indicates a failed injector coil.
• Fuel Injector Resistance (2012-2014 3.6L LFX Engine) — expected: 1.2 - 1.8 Ohms. Failure: A reading outside this range indicates an internal injector fault. These are low-impedance injectors and not interchangeable with the earlier LLT engine's injectors.
• Injector Circuit Voltage Spike (Inductive Kick) — expected: 60 - 80 Volts. Failure: Using an oscilloscope, the absence of this sharp voltage spike when the injector closes indicates a problem with the injector's coil or the PCM's driver circuit.
• Injector Pulse Width (at idle, warmed up) — expected: 2 - 4 milliseconds (ms). Failure: A value of 0 ms on cylinder 2 while other cylinders show normal pulse width suggests the ECM has disabled the injector due to a detected fault.

Scan Tool Commands That Help

• GDS2 (GM Dealer Tool) or high-end bidirectional scanner: Injector Balance Test — This test is crucial when a wiring or resistance test is inconclusive. The tool commands each injector to fire for a set duration and measures the corresponding drop in fuel rail pressure. If the pressure drop for cylinder 2 is significantly different from the others (GM specifies a variance of less than 20%), it confirms a flow issue with that injector.
• GDS2 or high-end bidirectional scanner: Cylinder Power Balance / Injector Kill — This function allows a technician to disable injectors one by one while monitoring engine RPM. When a healthy cylinder's injector is disabled, the engine's RPM will noticeably drop. If disabling cylinder 2 causes little or no change in RPM, it confirms that cylinder was not contributing power, pointing to a fault in its fuel or ignition system.

Wiring & Ground Locations

• Engine Control Module (ECM) — Typically located in the engine compartment. On some GM models of this era, it is mounted to the strut tower or near the airbox.. The ECM contains the driver circuit that grounds the fuel injector to activate it. All wiring for the injector circuit terminates at the ECM, making it a key testing point for continuity and shorts.
• G101 / G106 — G101 is located on the lower front of the engine block. It often jumpers to G106, located on the front center of the frame cross rail under the crank pulley.. G101 is a primary ground for the Engine Control Module (ECM). A poor or corroded ground at this location can cause a host of erratic electrical issues, including injector circuit faults.
• G102 — Located at the left rear of the engine.. This ground is primarily for the ignition coils. While not directly tied to the injector circuit, a poor ground here can cause misfires that might be confused with an injector problem during initial diagnosis.
• Injector Harness Chafe Points — As per TSB PIP4924D, inspect against the intake plenum, at valve cover bolts, against fuel lines, and on the side of the cylinder head under the plenum.. These are the most probable locations for a wiring short or open to occur, directly causing a P0202 code. Physical inspection of these specific areas is a critical first step.

OEM Part Supersession History

• 12642128 → 12634126 — Standard part update or revision by the manufacturer.
  Heads up: This part (12634126) is for the 2009-2011 LaCrosse with the 3.6L LLT engine. It is NOT compatible with the 2012-2014 LFX engine, which uses a different injector design and resistance.

Model Year Variations Within This Range

• 2009-2011: These models use the 3.6L LLT V6 engine, which features high-impedance fuel injectors (~12 Ohms), a Bosch ECM, and an aluminum intake manifold.
• 2012-2014: These models use the updated 3.6L LFX V6 engine. Key differences include low-impedance fuel injectors (~1.2-1.8 Ohms), a Delphi ECM, a composite intake manifold, and integrated exhaust manifolds. The injectors and ECM are not interchangeable with the earlier LLT models.