Code
P1290
CITROEN
P — Powertrain
Injector 1 control malfunction
AI status
Completed
Completed
100%
Causes
- Open or short in injector #1 wiring harness
- Corroded/loose connector at injector #1
- Failed injector (solenoid or piezo element)
- Faulty injector driver circuitry in the ECM
- Low battery/unstable supply voltage or poor ground
- Water/contaminant ingress into connector or injector
Symptoms
- MIL (check engine light) illuminated
- Rough idle or misfire on cylinder 1
- Loss of power or hesitation under load
- Hard starting or increased smoke (diesel)
- Poor fuel economy
- Possible engine vibration localized to cylinder 1
What to check
- Read and record all stored and pending codes and freeze-frame data with a scan tool
- Visual inspection of injector #1 wiring and connector for damage, corrosion, or oil/fuel contamination
- Check battery voltage and engine ground connections
- Measure injector #1 coil resistance (compare to spec) and inspect for open/short
- Check for continuity between injector connector and ECM pin with ignition off
- Backprobe connector while cranking or using a scope to verify drive waveform (pulse width, amplitude)
Signal parameters
- Injector coil resistance: typically provided in factory data (common range for solenoid injectors ~ 0.5–5 ohms; check vehicle spec)
- Drive voltage: battery voltage on supply rail, switching to ground or PWM by ECU
- Pulse width: variable with engine load/ECU strategy (milliseconds)
- Drive frequency: depends on engine speed and injection events
- Expected waveform: sharp switching edges, consistent duty cycle when commanded; no erratic noise or voltage collapse
Diagnostic algorithm
- Connect a professional scan tool. Record freeze frame, live data and any related codes (misfire, low rail, ECM errors). Clear codes and attempt to re-create fault.
- Visually inspect harness and connector at injector #1 for corrosion, bent pins, oil/fuel contamination or physical damage. Repair as needed.
- With ignition off, measure injector #1 coil resistance and compare to factory spec. Note: piezo and solenoid injectors differ—use correct spec.
- Check supply and ground circuits at the injector connector for battery voltage and good ground continuity to the ECU ground.
- Backprobe the injector connector and use an oscilloscope (preferred) or DVOM while cranking and during an ECU commanded injector test to observe waveform, pulse width and voltage levels.
- If wiring and signals are good but injector shows abnormal behavior, perform an injector bench test or swap injectors with a known-good cylinder to see if the fault follows the injector.
- If the fault follows the injector, replace the injector. If the fault remains on the same cylinder after swapping, further inspect harness and ECM driver circuit.
- If wiring harness and injector are good, suspect ECM driver failure. Confirm with manufacturer diagnostic procedures before replacing ECM—check for software updates and perform ECM bench tests if available.
- After repairs, clear codes and road-test. Re-scan to verify that P1290 does not return and that related drivability issues are resolved.
Likely causes
- Damaged or chafed wiring to cylinder 1 injector
- Corrosion or bent pins in the injector connector
- Injector coil broken or shorted
- Failed injector driver transistor inside ECM
- Intermittent supply or ground at the injector circuit
Fault status
Status
P1290 - Injector #1 control malfunction. ECM detected abnormal signal or driver fault on injector 1 circuit. Code stored; further diagnostic testing required.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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