Code
P1289
CITROEN
P — Powertrain
Injector 1 control malfunction
Views:
UK: 3
EN: 6
RU: 7
AI status
Completed
Completed
100%
Causes
- Open or short in injector 1 wiring (open to circuit, short to ground or battery)
- Corroded/poor connector or pin at injector
- Faulty injector (stuck, shorted coil, internal failure)
- Failed or intermittent injector driver inside the engine ECU
- Blown fuse or faulty relay feeding injector circuit/ECU power
- Poor engine/ECU ground or low battery/supply voltage
Symptoms
- Malfunction Indicator Lamp (MIL) on (check engine light)
- Rough idle or vibration, especially at idle
- Misfire felt or recorded on cylinder 1
- Poor engine performance, hesitation or lack of power
- Increased fuel consumption or black smoke from exhaust
- Difficult or extended cranking/start issues on some vehicles
What to check
- Read freeze frame and live data—look for misfire counters, injector pulse width and fuel trim values for cylinder 1
- Visually inspect injector 1 connector and wiring for damage, corrosion, pins pushed out or water ingress
- Check battery voltage and main power/ground feeds to the ECU and injector rail; confirm fuses/relays for fuel/injectors are OK
- Measure injector 1 coil resistance with meter (engine off, connector disconnected)
- Backprobe injector connector with oscilloscope or lab scope to view driver waveform during cranking and running
- Swap injector 1 with another cylinder’s injector (if identical) to see if fault follows the injector or stays with cylinder
Signal parameters
- Supply voltage to injector: approx. battery voltage (~11–14.5 V) when key ON (varies by vehicle)
- Injector coil resistance (typical ranges): low-impedance injectors ~2–6 Ω; high-impedance injectors ~12–16 Ω — verify OEM spec for the vehicle
- Driver behavior: low-side driver commonly switches injector to ground; idle waveform is a near-square pulse with a falling edge when activated
- Pulse width: typically from about 1 ms (light load) to >10 ms (cold start/high load) — depends on engine operating conditions
- Current during activation: typically up to several amps for low-impedance injectors; exact current depends on injector type and pulse width
- If using a scope: expect consistent pulses for each injection event; missing pulses, clipped or noisy waveform, or persistent high/low voltage indicate problem
Diagnostic algorithm
- Retrieve and record all stored codes and freeze frame data. Note misfire counters and operating conditions when the code set.
- Visually inspect injector 1 connector and harness for corrosion, damage, pin fit, water or oil contamination. Repair any visible damage.
- Check fuses and relays related to fuel injectors/ECU power. Verify stable battery voltage and engine ground integrity.
- With ignition OFF, disconnect injector 1 and measure injector coil resistance. Compare to OEM specification or the typical ranges listed; replace if out-of-spec.
- Check continuity between the injector connector pin and ECU connector pin. Verify no short to ground or battery. Repair any wiring faults.
- With a lab scope or break-out probe and engine cranking/running, inspect injector 1 waveform. Look for missing pulses, abnormal voltage spikes, or driver clipping.
- Swap injector 1 with a known-good injector from another cylinder (if identical). Clear codes and run engine. If the code follows the injector, replace the injector.
- If the fault remains on cylinder 1 after swapping injectors, suspect the wiring or ECU driver. Re-check continuity, grounds and perform wiggle tests to reproduce the fault.
- If testing indicates a failed injector driver in the ECU, consult manufacturer guidance — ECU repair or replacement may be required. Confirm with controlled bench tests where possible.
- After repairs, clear codes, re-test the vehicle under the same conditions that produced the fault and confirm proper operation and that the MIL remains off.
Likely causes
- Damaged or corroded injector connector on cylinder 1
- Open/short in the harness between injector 1 and ECU
- Failed low-side injector driver in ECU for channel 1
- Injector coil internal short or open
- Intermittent connection due to vibration or damaged pin
Fault status
Status
Injector 1 control circuit malfunction detected by engine control module — possible wiring, connector, injector or ECU driver fault. MIL illuminated.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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