Code
P029C
Generic
P — Powertrain
Cylinder 1 - Injector Restricted
AI status
Completed
Completed
100%
Causes
- Clogged or partially blocked fuel injector (deposits, varnish, debris)
- Restricted fuel supply to injector (collapsed/plugged in-rail filter or line)
- Internal injector mechanical failure (sticking pintle, collapsed filter screen)
- Low fuel rail pressure or intermittent pressure drop
- Contaminated fuel (sediment, rust, water)
- Injector wiring/connectors poor contact or PCM driver fault causing reduced duty/current
Symptoms
- Rough idle or vibration, especially at idle
- Loss of power, hesitation or poor throttle response
- Engine misfire reported for cylinder 1 (may set P0301 alongside)
- Reduced fuel economy and increased emissions
- Check Engine Light (MIL) illuminated; drivability faults under load or idle
What to check
- Read freeze frame and live data with a scan tool (injector pulse width, fuel trims, misfire counts)
- Check for related codes (P0201, P0301, P0200, P0261) and note any patterns
- Inspect fuel quality and fuel filter condition; check for contaminants or rust
- Measure fuel rail pressure and regulator operation under idle and load
- Visually inspect injector connector and wiring for corrosion, bent pins, or damage
- Measure injector resistance and compare to specification
Signal parameters
- Injector pulse width (ms) for cylinder 1
- Injector duty cycle (%)
- Injector electrical resistance (ohms)
- Fuel rail pressure (psi / bar) and pressure fluctuation
- Short-term and long-term fuel trim (STFT/LTFT)
- Cylinder 1 misfire counter / PIDs
Diagnostic algorithm
- Retrieve and document freeze frame, all stored codes and live data. Note when the fault occurs (idle, cold start, load).
- Visually inspect injector connector, harness and fuel rail near cylinder 1 for damage, corrosion or debris. Repair as needed.
- Verify fuel supply: check fuel filter condition and fuel rail pressure under key on, idle and load. Replace clogged filter and retest.
- Compare injector electrical values: measure resistance of cylinder 1 injector and compare to bank mates. Check for open/short.
- Use a noid light or scope to confirm proper injector drive pulse from PCM (pulse width and amplitude). Rule out PCM driver issues.
- Perform a cylinder balance or cylinder contribution test (deactivate injector 1 briefly) to confirm lower flow or abnormal contribution.
- If electrical and supply systems are OK, remove injector 1 and inspect tip and inlet screen for deposits/debris. Consider ultrasonic cleaning or service if contaminated.
- If cleaning does not restore proper flow, bench test or replace the injector. Reinstall and verify with live data and road test.
- After repair, clear codes and verify the fault does not return and that trims, misfires and performance are normal.
Likely causes
- Carbon or varnish buildup inside cylinder 1 injector restricting flow
- Blocked injector inlet screen or debris in fuel rail near cylinder 1
- Weak/erratic fuel rail pressure causing insufficient flow to that injector
- Damaged injector (sticking/partial internal blockage) on cylinder 1
Fault status
Status
Cylinder 1 fuel injector flow restricted — reduced injector flow detected for cylinder 1.
Repair difficulty: Medium
Diagnostic time: 1.5 - 3.0 hours
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