Code
P0291
HUMMER
P — Powertrain
Cylinder 11 Injector Circuit Low
Views:
UK: 13
EN: 19
RU: 16
AI status
Completed
Completed
100%
Causes
- Short to ground on the cylinder 11 injector control wire
- Corroded, damaged or loose connector at injector #11
- Failed injector (internal short or shorted driver coil)
- Open/shorted wiring between injector and ECM/PCM
- Faulty ECM/PCM driver transistor for injector #11
- Blown fuse or faulty relay supplying injector bank
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Rough idle or misfire on cylinder 11
- Reduced engine power or hesitation under load
- Poor fuel economy and increased emissions
- Hard starting or extended crank time
- Occasional smoke or abnormal exhaust behavior (diesel engines)
What to check
- Read and record all DTCs and freeze-frame data with a scan tool
- Verify battery and charging system voltage (12–14 V)
- Visually inspect injector #11 connector, pins and wiring for damage, corrosion or water intrusion
- Back-probe the injector connector while cranking/idle and observe voltage with a DVOM or scan tool live data
- Check injector resistance with an ohmmeter and compare to specification
- Perform a wiggle test on wiring harness while monitoring signal to look for intermittent faults
Signal parameters
- Injector supply/reference: ~battery voltage (≈12–14 V) present at supply pin with ignition ON
- Control/driver pin (low-side) expected idle/high near supply voltage when not driven, and pulsed low (~0–1 V) when the ECM activates the injector
- Pulse width/frequency varies with engine load and RPM (milliseconds pulse width at idle, wider under load)
- Typical solenoid injector coil resistance: commonly ~1–14 ohms (varies by engine and injector type) — consult OEM spec
- A steady near-0 V on the control line when not commanded indicates a short to ground; no change (open/high) indicates open circuit
Diagnostic algorithm
- Confirm DTC and note freeze frame/warm-up conditions; erase codes and reproduce if needed.
- Check battery voltage and charging; low system voltage can cause erroneous readings.
- Visually inspect connector and wiring at cylinder 11 for damage, corrosion or pins pushed out; repair as needed.
- Back-probe injector connector: with ignition ON verify reference/supply voltage; with engine cranking or running observe the control pin for pulsed activity. Record voltages.
- Measure injector coil resistance. If resistance is far out of spec, replace injector.
- With injector disconnected, check for short to ground on the control circuit (ohmmeter to chassis ground) and for short to power. Repair any short/open in harness.
- Swap the suspect injector with another cylinder (if numbering and engine design allow) and see if the code follows the injector (indicates bad injector) or remains on cylinder 11 (indicates wiring/ECM issue).
- Use an oscilloscope to inspect the injector drive waveform for correct switching behavior and current draw if available.
- Inspect and test PCM/ECM driver outputs and PCM grounds; if all external wiring and the injector test good, consider PCM fault and follow manufacturer procedure for PCM testing or replacement.
- After repair, clear codes and road-test to confirm repair; re-check for intermittent faults under load and different environmental conditions.
Likely causes
- Damaged connector or wiring at injector #11 (pin corrosion, chafing, exposed conductor)
- Short to ground in the injector control circuit caused by harness damage
- Failed injector with internal electrical fault
- Failed ECM/PCM output driver for that injector circuit
Fault status
Status
Injector circuit low detected for cylinder 11 — low-voltage condition on the injector control circuit. Possible short to ground, wiring/connector fault, failed injector, or ECM driver failure.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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