Code
P1188
CITROEN
P — Powertrain
Multifunction double relay control malfunction
AI status
Completed
Completed
100%
Causes
- Failed or sticking multifunction relay (dual relay pack)
- Blown fuse protecting the relay circuit
- Open, shorted or corroded wiring/connector to the relay
- Poor ground at the relay or ECU/module
- Faulty ECU / relay driver transistor inside the module
- Intermittent connection due to vibration or moisture
Symptoms
- MIL/check engine lamp illuminated
- Loss or intermittent operation of one or more functions controlled by the multifunction relay (example: fuel pump, cooling fan, fuel injection feed, accessories — vehicle-specific)
- Hard starting or no-start if fuel pump feed is affected
- Cooling fan may not run causing higher-than-normal engine temperature
- Intermittent electrical faults or component shutdowns tied to the relay outputs
What to check
- Read and record freeze-frame and live data with a capable scan tool; note related pending or permanent codes
- Identify which circuits/functions the multifunction double relay controls using the vehicle wiring diagram
- Visually inspect relay, fuse(s), connector, and wiring for damage, corrosion, or loose terminals
- Check relevant fuse(s) for continuity and correct rating
- Verify battery voltage at the relay power input (key ON) and good chassis/body ground at relay
- Back-probe/control-pin the relay connector to observe control signal (voltage or ground) from the module while commanded ON/OFF
Signal parameters
- Relay coil/control voltage with key ON/engine OFF: nominal battery voltage (~12 V) at supply pin
- ECU control output to relay: either ground-switching (0 V) or positive switching (≈12 V) when commanded
- Relay coil resistance (ohms) — compare to specification for the relay
- Output circuit voltage to controlled loads when relay energized: near battery voltage under no-load conditions
- Ground resistance between relay ground and battery negative (should be low,
- Current draw through relay output when driving load (compare to expected load current)
Diagnostic algorithm
- Retrieve full code list and freeze frame data with scan tool; clear codes and attempt to re-create to confirm fault.
- Consult the vehicle-specific wiring diagram to locate the multifunction double relay, fuses, and associated control pins on the ECU/BODY module.
- Visually inspect the relay, fuse(s), connectors, and wiring harness for obvious damage, corrosion, or water ingress; repair as needed.
- Check fuses in circuit for continuity and correct amperage; replace if blown and retest.
- With ignition ON (engine OFF), measure battery voltage at the relay supply pin and the voltage at the relay output pin while the relay is not energized. Command the relay ON from the scan tool and observe voltage changes at control and output pins.
- Back-probe the control pin to confirm the ECU sends the correct command signal (switches to ground or supply) when the function is requested; check for intermittent or weak signals while operating the function.
- Measure coil resistance of the relay (bench) or substitute a known-good relay to confirm relay operation. If replacement cures the code, retest to confirm.
- If relay and fuses are good but control signal is absent or incorrect, inspect wiring between ECU and relay for opens/shorts/high resistance and repair wiring/connectors as required.
- If wiring and external components test good, suspect internal driver failure in the ECU/body module. Verify with manufacturer diagnostic procedures before replacing module; consider confirmed module replacement or reprogramming where applicable.
- After repairs, erase codes and perform functional test cycles and a road test to confirm the fault does not return.
Likely causes
- Corrosion or loose terminals at the relay connector causing intermittent contact
- Failed relay contacts or coil in the dual relay assembly
- Blown or high-resistance fuse in the relay feed or ECU supply
- Damaged wiring harness (chafing, pinched, rodent damage) causing short to ground or open circuit
- Failed driver stage inside the powertrain or body control module
Fault status
Status
Multifunction double relay control malfunction detected — control circuit, relay, wiring, or module fault present.
Repair difficulty: Medium
Diagnostic time: 0.5 - 2.0 hours
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