GM Duramax P0202: Injector Circuit Open - Cylinder 2
P-Code P0202 (FMI N/A) — Injector Circuit/Open - Cylinder 2
Quick Answer
P0202 means the GM Duramax PCM has detected an open circuit in the cylinder 2 injector control circuit. It's a High severity fault causing a rough idle and misfire, but it does not shut the engine down.
Overview: GM Duramax P-Code P0202
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.
Repair Snapshot
Time
1.5 - 3 Hours
Difficulty
Intermediate
Parts Cost
$60 - $700
Dealer Labor
$550+
Tools Required
- GM Tech2Win/GDS2
- Multimeter
- Snap-on NEXIQ
- Diesel Laptops Diagnostic Software
What P-Code P0202 Means
P0202 means the PCM has detected an open circuit in the fuel injector control circuit for cylinder 2 on the Duramax, so that injector can't be fired. The truck runs rough with a noticeable single-cylinder misfire and the MIL illuminates, but it's not a shutdown code. Extended operation with a dead cylinder can eventually wash fuel into the oil.
Symptoms Drivers Notice
- Rough idle with a miss traceable to cylinder 2
- MIL illuminated, sometimes flashing under an active misfire
- Reduced power and fuel economy
- Possible diesel smell from unburned fuel
Most Likely Root Causes
Chafed injector harness wire near the valve cover
CommonEngine vibration wears through wire insulation where the harness routes close to valve cover hardware, eventually breaking the conductor.
Corroded or loose injector connector
CommonMoisture intrusion or a partially disengaged locking clip creates a high-resistance or open contact that reads as a dead circuit.
Failed injector solenoid winding
OccasionalThe internal solenoid coil can fail from heat and vibration fatigue over extended service life.
PCM injector driver circuit failure
RareAn internal PCM fault on that specific driver channel would produce the same code, but only after the injector and harness both test clean.
Common Misdiagnoses (Don't Waste Parts)
Replacing the injector without checking harness continuity first
Why it happens: A parts-cannon shortcut assumes the injector is the failure point since it's the named component in the code description.
Do this 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
Why it happens: Rough idle symptoms get blamed on fuel delivery generally without pulling codes first.
Do this 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
Why it happens: A quick visual check can miss a connector that looks plugged in but isn't fully seated.
Do this instead: Physically confirm the connector cannot be pulled apart by hand before moving to more invasive diagnostics.
Master Tech Commentary
Mechanic's Notes
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.
Step-by-Step Diagnostic Procedure
- Step 1: Scan for codes with GM Tech2Win/GDS2 or a comparable tool and confirm P0202, checking for accompanying misfire codes on the same cylinder.
- Step 2: Shut the engine off and unplug the cylinder 2 injector connector, inspecting for corrosion, bent pins, or a partially disengaged locking clip.
- Step 3: Measure resistance across the injector solenoid terminals with a multimeter and compare the reading to Duramax spec for your model year.
- Step 4: If the injector reads good, check harness continuity from the connector back to the PCM, inspecting for chafing near the valve cover.
- Step 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.
Live Data & Freeze-Frame Tips
Run a cylinder balance or contribution test with GDS2 or Diesel Laptops and confirm cylinder 2 shows zero or near-zero RPM contribution. Watching injector driver voltage helps distinguish a clean open circuit from a PCM-side fault before disassembly.
Safety Warnings
- 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.
When to Limp In vs Tow
Towing is generally not needed since the truck will still drive with a rough idle and reduced power. Consider towing if additional misfire or fuel rail pressure codes appear alongside it.
Prevention Tips for Fleets & Owner-Operators
- 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.
Related Fault Codes
P0201
Same fault type but for the cylinder 1 injector circuit.
P0300
Random/multiple cylinder misfire detected, which can accompany a single injector circuit fault if multiple cylinders are affected.
P2149
Fuel injector group supply voltage circuit fault, worth checking if multiple injector codes appear together.
Frequently Asked Questions
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.
How much does it cost to fix an open injector circuit?
If it's a harness repair, cost can be under $200; if the injector itself needs replacing, expect to pay several hundred dollars in parts alone on a Duramax.
Can a bad ground cause this code?
Yes, since injector solenoids are grounded through the PCM driver circuit, a corroded or broken ground path reads identically to an open supply wire on a resistance test.
Is it okay to keep driving a few days with a dead cylinder?
Short-term driving is generally fine, but extended operation with a disabled cylinder risks fuel washing down the cylinder wall and diluting engine oil, so timely repair is worthwhile.