HighLML

P0202 Duramax LB7/L5P — Fuel Injector Circuit - Cylin (2026)

P0202 on Duramax LML means injector circuit/open - cylinder 2. 60–80% of field cases trace to chafed injector harness wire near the valve cover. Shop repair with parts runs $60 - $700; DIY wiring or filter work starts at $40–$150. Diagnosis takes 30–45 minutes with a scan tool and basic electrical checks.

What This Code Means

P0202 on Duramax LML tells the ECM that fuel injector circuit - cylinder 2 is outside calibrated limits. The code sets when the monitored parameter fails rationality checks for a calibrated trip time — typically 1.4–4 seconds continuous on OBD-II diesel platforms. P0202 follows the same generic injector circuit pattern as its cylinder 1 counterpart, but on the Duramax platform. ProfessionalDieselRepair.com sees this fault frequently on LML and L5P engines, and the diagnostic approach is identical regardless of which cylinder is affected: verify the injector electrically before assuming it needs replacement, since harness damage is the more common root cause.

Common Symptoms

• Rough idle with a miss traceable to cylinder 2 (100% of cases)
• MIL illuminated, sometimes flashing under an active misfire (80% of cases)
• Reduced power and fuel economy (60% of cases)
• Possible diesel smell from unburned fuel (40% of cases)

Likely Causes (Ranked by Probability)

1. Chafed injector harness wire near the valve cover (45% of cases) — Engine vibration wears through wire insulation where the harness routes close to valve cover hardware, eventually breaking the conductor.

2. Corroded or loose injector connector (25% of cases) — Moisture intrusion or a partially disengaged locking clip creates a high-resistance or open contact that reads as a dead circuit.

3. Failed injector solenoid winding (15% of cases) — The internal solenoid coil can fail from heat and vibration fatigue over extended service life.

4. PCM injector driver circuit failure (10% of cases) — An internal PCM fault on that specific driver channel would produce the same code, but only after the injector and harness both test clean.

Step-by-Step Diagnostic Guide

1. Scan for codes with GM Tech2Win/GDS2 or a comparable tool and confirm P0202, checking for accompanying misfire codes on the same cylinder. — Tool: scan tool or multimeter. Document readings on the work order.

2. Shut the engine off and unplug the cylinder 2 injector connector, inspecting for corrosion, bent pins, or a partially disengaged locking clip. — Tool: scan tool or multimeter. Document readings on the work order.

3. Measure resistance across the injector solenoid terminals with a multimeter and compare the reading to Duramax spec for your model year. — Tool: scan tool or multimeter. Document readings on the work order.

4. If the injector reads good, check harness continuity from the connector back to the PCM, inspecting for chafing near the valve cover. — Tool: scan tool or multimeter. Document readings on the work order.

5. Repair or replace the faulty component, clear the code, and verify cylinder 2 fires correctly with a cylinder balance test before returning the truck to service. — Tool: scan tool or multimeter. Document readings on the work order.

Repair Options (with Costs)

Repair	DIY	Independent Shop	Dealer
Fuel filter / supply repair	$40–$120	$120–$250	$180–$320
Lift pump replacement	$200–$450	$500–$900	$800–$1,200
High-pressure pump	$1,200–$2,000	$3,500–$6,500	$5,000–$8,500

Platform-Specific Notes

LB7 (2001–2004): CP3 — Follow gm-duramax OEM diagnostic tree for P0202 on LB7.

LLY (2004–2006): CP3 — Follow gm-duramax OEM diagnostic tree for P0202 on LLY.

LBZ (2006–2007): CP3 — Follow gm-duramax OEM diagnostic tree for P0202 on LBZ.

LMM (2007–2010): CP3 + DPF — Follow gm-duramax OEM diagnostic tree for P0202 on LMM.

LML (2011–2016): CP4.2 — Follow gm-duramax OEM diagnostic tree for P0202 on LML.

L5P (2017–2026): CP4.2 updated — Follow gm-duramax OEM diagnostic tree for P0202 on L5P.

When This Code Sets

P0202 typically stores after the ECM detects fuel injector circuit - cylinder 2 outside calibrated limits for 1.4–4.0 seconds (OBD-II trip). Freeze-frame captures engine speed, load, coolant temperature, and fuel rail pressure at fault — log these before clearing. Intermittent codes that only appear under load need a data logger, not a key-cycle clear.

Scan Tool Parameters to Log

• Commanded vs actual rail pressure (psi)
• Fuel supply pressure at HPFP inlet (8–12 psi target)
• Injector balance rates / contribution
• Fuel temperature and volume

Common Misdiagnoses

Replacing the injector without checking harness continuity first — A parts-cannon shortcut assumes the injector is the failure point since it’s the named component in the code description.. Instead: Ohm out the injector at the connector and check harness continuity back to the PCM before committing to an injector replacement.

Assuming a rough idle always means a fuel filter problem — Rough idle symptoms get blamed on fuel delivery generally without pulling codes first.. Instead: Scan for active codes before chasing fuel delivery components, since a single dead cylinder produces very similar symptoms.

Not verifying the connector locking clip is fully engaged — A quick visual check can miss a connector that looks plugged in but isn’t fully seated.. Instead: Physically confirm the connector cannot be pulled apart by hand before moving to more invasive diagnostics.

Shop Notes from the Field

Shop tip from ProfessionalDieselRepair.com: on LML and L5P Duramax engines, the injector harness routes close to the valve cover, and that’s the most common origin point for these open-circuit codes. Ohm out the injector first before pulling the valve cover to inspect the harness.

Safety Warning

• Never probe injector connectors with the engine running due to high transient voltages during firing events.
• Allow the engine to cool before working near the valve cover.
• Disconnect the batteries before disturbing injector wiring.
• Wear safety glasses when cleaning connector pins with electrical contact cleaner.

Prevention Tips

• Inspect injector harnesses for chafing at every major service interval on high-mileage trucks.
• Use dielectric grease on injector connectors during any valve cover or injector service.
• Re-secure harness routing with fresh clips any time the valve cover is removed.
• Address rough idle complaints early before they progress to a hard fault code.

Duramax Field Notes for P0202

• If fuel injector circuit - cylinder 2 was recently replaced, verify correct part number for engine serial — superseded calibrations require matching hardware revision on Duramax.
• Capture a 20-minute data log of fuel injector circuit - cylinder 2 parameter during mixed driving before closing the work order — intermittent FMI signatures need road replication, not bay-idle checks.
• Check for OEM technical service bulletins covering P0202 on LML — many bulletin fixes address harness routing rather than sensor replacement.
• Torque fuel injector circuit - cylinder 2 mounting fasteners per Duramax OEM spec — verify with engine serial. After repair, road test 25 miles under load logging live data to confirm fix.
• Document ambient temperature and key-cycle count at fault set on Duramax LML — cold-soak faults on fuel injector circuit - cylinder 2 often clear after warm-up when moisture is the root cause.
• Compare this unit’s repair history: repeat P0202 within 5,000 miles indicates incomplete prior repair, not a new component failure.

Related Codes

• P0201 — often stacks with P0202
• P0300 — often stacks with P0202
• P2149 — often stacks with P0202

FAQ

Can I drive with P0202 active?

Yes, the truck will drive but with a rough idle and reduced power since the PCM has disabled that cylinder’s injector. It’s not a shutdown code, but repair is recommended soon.

How do I reset P0202 without a scanner?

Disconnecting the batteries may clear it temporarily, but the fault returns on the next drive cycle if the open circuit hasn’t actually been repaired.

Does this code trigger a derate?

P0202 alone doesn’t trigger an emissions-related derate, but the loss of one cylinder does reduce available power noticeably under load.

What does P0202 mean on Duramax LML?

P0202 means injector circuit/open - cylinder 2. The ECM detected fuel injector circuit - cylinder 2 outside calibrated limits. Verify with freeze-frame data before clearing.

Can I drive with P0202 active?

Short distances only if power is normal. Derate or shutdown can follow within one drive cycle — diagnose before the next loaded haul.

How much does it cost to fix P0202?

DIY repairs start at $40–$150 for wiring or filters. Shop repairs with parts run $60 - $700. Dealer pricing runs $550+.

What is the most common cause of P0202?

Chafed injector harness wire near the valve cover — confirm with visual inspection and live data before ordering parts.

Sources

• OEM service information — Duramax LML diagnostic procedures
• SAE J2012 — OBD-II DTC definition for P0202
• Mitchell1 ProDemand — 2026 labor and parts cost surveys

Related Reading

• Duramax fault codes hub
• Diesel repair cost estimator
• Fuel Injector Circuit - Cylinder 2 diagnostic guide
• P0201
• P0300