VOLVO
CEM-U023187 - Lost Communication With Rain Sensing Module. Bus Signal / Message Failures. Missing message
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
7 modelsS60 (2011–), S80 (2007–), V60 (2011–), V60 Cross Country (2015–), V70 (2008–), XC60 (2009–), XC70 (2008–)
What does this fault code mean?
The fault code means that the central electronic module (CEM) gets no reply from the rain sensor (RSM) on the LIN network, a simpler network used for small sensors. The rain sensor may then stop responding to rain, so the wipers do not start automatically. The fault concerns communication on the LIN network and is not always the sensor itself.
Possible causes
- Break in the supply to the rain sensor (RSM)
- Broken earth wire between the rain sensor and the body
- Poor contact in the connections
- Leaking battery acid in the siren disturbs the LIN network
- The rain sensor itself is faulty
- The cause may lie in the LIN network serving the interior movement sensor, heartbeat sensor or siren
What you can do
- 1Switch the ignition off and check the supply wire from the CEM to the rain sensor for breaks and shorts to ground
- 2Check the ground wire between the rain sensor and the ground point for breaks
- 3Check the signal wire for intermittent shorts to ground or breaks, and check contacts for resistance and oxidation
- 4Switch the ignition on and read the rain sensor part number with a diagnostic tool. If it reads, communication works at that moment
- 5Do not replace the rain sensor until the wiring is checked and no relevant fault codes from the movement, heartbeat or siren sensors are set
Symptoms you may notice1
- Rain sensor does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.