Citroen C3 & C2 Water Damaged ECU

The Citroen C2 and C3 vehicles commonly experience engine Electronic Control Unit (ECU) malfunctions due to water ingress, leading to various issues such as engine cutting out, misfiring, poor running, and refusal to rev. The problem typically arises from coolant system fluid entering the main engine wiring harness, ultimately reaching the ECU and causing corrosion of its internal terminals.

The symptoms of this ECU malfunction include cutting out, poor rev range, limp mode activation, misfires, and the illumination of the engine management light. While fault codes may suggest problems with throttle position, engine misfire, or temperature/O2 sensors, the root cause is often the corrosion of ECU terminals.

Solution

• Service for this system type is no longer offered. Options include purchasing a new ECU from the main dealer or acquiring a used replacement. If opting for a used unit, the key coding should be transferred from the original ECU using dealer-level diagnostic equipment.

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Common Failure Symptoms

• Cutting out
• Poor rev range
• Limp mode activation
• Misfires
• Engine management light illumination

Common Fault Codes

• P0121 – Throttle Signals 1 And 2 Incoherence
• P1161 – Throttle Position Implausible Signal
• P0123 – Throttle Position Sensor
• P2176 – Motorised Throttle Programming
• P1340 – Multiple Misfire Detected
• P0135 – O2 Heater Circuit
• P0115 – Coolant Temp Sensor Fault
• P1631 – ECU Internal Malfunction

Affected Vehicles

• Citroen Berlingo 2002 – 2011
• Citroen C2 2003 – 2011
• Citroen C3 2002 – 2011

Common Failing Part Numbers

• 21585598-3 A0 / 21585675-3 A0 / 21585768-5 A0 / 21585784-1 A0 / 21585785-4 A / 215859001 A0 / 21585932-9 A / 21585984-5 A / 21586048-9 A / 21586048-9A / 215862398B / 21586539-8A / 21586562-9 A / 21586563-2 A / 21586877-0 A
• 6011 150061 / 6053 215016 / 6100 269889 / 6192 553788 / 6192 553788 / 6275 618804 / 6287 628749 / 7052 754374 / 7288005632 / 7332 434979 / 8119 003131 / 8154 141 206 / 8184 161516 
• HW9651696680 / HW965583280 / HW9655883280 / HW9655883280 / SW9660374680 / SW9661191880 / SW9661700480 / SW9661960880 / SW9661961280 / SW9661978880 / SW9663306680 / SW9663394480 / SW9663717680 / SW9664127180 / SW9664242980 / SW9664637080 / SW9665424480 / SW9665666980 / SW9665799180 / SW9666257580 / SW9666262880

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