Central Electronic Module (CEM) is the main electrical module on Volvo vehicles that communicate with the rest of your car's modules and components. When it fails, it can cause unpredictable intermittent electrical problems.
It is a lot cheaper to get your Volvo CEM rebuilt service which you can order on eBay instead of getting it replaced by the dealer.
2001 through 2013 Volvo vehicles are prone to intermittent electrical problems due to water getting to the Central Electronic Module.
Corrosion on the CEM terminals can develop if you:
- live in a humid climate,
- forget the windows open when it rains
- if your vehicle has been in flood.
For example, you may experience an engine turning off on its own or doesn't start. Random warning lights coming such as ABS, airbag, brake warning. The keyless entry is not working.
Getting the CEM module replaced by the dealer costs $1000+. A cheaper solution would be to repair your existing module. Remove your existing module and send it for repair to a facility that offers Volvo CEM Module Repair on eBay.
A CEM module (or corroded connections at CEM) triggers intermittent electrical problems.
Here are some problems you may notice.
- Security System not working
- Brake, please make a safe stop error on the dashboard.
- Ignition issues, can't start the car.
- Waring Lights Come On / Indicators failure.
- Wipers turn on randomly.
- Steering wheel hard to turn.
- Instrument cluster lights turn on.
- Gauges don't work
- Radio works intermittently
- Accessories stop working
- Lights don't work intermittently.
- Wipers do not work or come on sporadic.
- CAN comms fault on the diagnostic tool
- ABS light comes on randomly
- No communication with the CEM unit
- Brake failure
- Limp mode
- Not start
- Immo fault
- Engine Cutting Out Randomly
These are some of the most common issues. Keep in mind you may only experience one or two of these symptoms, depending on how and where your CEM has failed. Several of these problems may be due to a defective body control module or Light Control Module (LCM).
The car may work fine when cold but develops random electrical problems when hot, cold, or humid.
How to Diagnose Volvo CEM Module
To troubleshoot Volvo's electrical problem, you can start by reading the fault codes from the CEM module. You will need a Volvo scanner as generic OBD2 scanners can't read CEM fault codes. This video shows you how to read and clear codes from the Volvo CEM module using iCarsoft for Volvo.
If you cannot establish communication with the CEM module, the terminals at the module may be corroded. You can remove the module and inspect it. If you cannot repair it yourself, send it to a third-party service that fixes the Volvo CEM module.
How to remove and clean Volvo CEM
Here are the instructions on how to remove and clean the Volvo CEM module.
- Disconnect the battery. If your battery is in the engine bay, open the hood by pulling the hood release under the dashboard. Use a 10mm socket to disconnect the negative battery terminal. If you don't have a battery in the engine bay, the battery will be in the trunk below the floor carpet. Open the trunk. Lift the carpet. Remove the metal plate on top of the battery, then disconnect the negative battery terminal.
- Locate the CEM module under the dashboard on the passenger side for 2003 to 2013 models. In 1999 - 2004 XC90, XC70, V70, S60, S80 CEM are under the driver's side dashboard.
- Remove the kick panel or fabric cover under the dash. You will need to remove plastic retainers to pull down the cover.
- Now the CEM module is exposed. Twist two screws on the CEM and pull down the module.
- Disconnect the electrical connectors from the CEM. To remove the connectors, first, pull back the lever to unlock it, then lift it out.
- Disconnect the electrical connections from the bottom of the CEM module as well.
- Inspect the connectors and pins on CEM for corrosion.
- Remove the black relays from the CEM and inspect them as well.
- Use a small brush to clean the contacts in combination with the contact cleaner.
- Once you have cleaned all the contact, allow the CEM to dry completely.
- Apply a light coat of electronic contact protector (dielectric grease) on each terminal to improve conductivity.
- Reconnect all connectors to the CEM. Each connector has a unique shape and, therefore, will only go into its own port.
- Secure the CEM on the two brackets that are under the dashboard.
- Tighten the two screws
- Install the cover under the dashboard.
- Reconnect battery negative terminal.
- Start the car and verify everything is working properly.
Frequently Asked Questions
My car won't start after cleaning the CEM.
Check that the connectors to the CEM are fully inserted and locked properly. Check the battery negative terminal is tightened.
Which Volvo models have this problem?
Primary Volvos on the P1 platform. Volvos from 2004 to 2013 have a CEM module under the dashboard on the passenger side.
Which cars are Volvo cars based on the P1 platform?
2004-2012 Volvo S40 II (P11)
2004-2012 Volvo V50 (P12)
2006-2013 Volvo C70 II (P15)
2007-2013 Volvo C30 (P14)
Does this problem affect other cars?
Yes. This problem can affect other cars based on the P1 platform. Examples include Ford C1 models such as Focus, Kuga, Escort, Escape, Transit, Linkon MKC, Mazda Alexa, Mazda3, Biante. Sabb vehicles as well.