As vehicles become more advanced, they need more control modules. Finding places in the car to put the growing number of control modules brings more challenges to manufacturers, and they become more inventive in finding places to put them in. This brings it's own special problems that here at the help desk we are seeing more and more.
A case this week was a workshop calling us about a 2005 Renault Grand Scenic with an electronic parking brake fault. Returning a code C1171 : Operating unit data mismatch. Unable to get sensible data from the EPB system, a wiring diagram was requested. Armed with the diagram, the mechanic traced the circuits to a water damaged connector under the passenger seat. Water had been leaking in through the roof and pooling under the seat, causing severe damage to the wiring.
Another example was a 2004 Audi A4 with central locking and window problems. The windows kept coming down on their own, the central locking was opening intermittently and the alarm was triggering during the night. As this is a known problem, we directed the mechanic to look under the passenger seat, where the comfort module is located. As he lifted the carpet, not only was the module under water, the loom had also corroded away, prompting a new module and a new wiring loom termination connector. As the cause was blocked drains in the scuttle below the battery, a good flush of all the leaves blocking the drains was also required.
A 2004 Golf 1.6 went into limited throttle operation, and was returning trouble codes for pedal coherence after a valeting. The mechanic installed a new pedal, without testing for correct signals. No joy. He did not have a scope to test correctly so he called us for advice. After a test plan was explained on the pedal,it was found that the 5 volt Reference was missing at the pedal and the throttle valve position sensor. He went to check the ECM under the front scuttle: water, water, everywhere. Blocked drains and a pressure washer had killed the control module.
A non-starting Renault Clio was brought into a garage. The mechanic was unable to communicate with the Body System Interface (BSI), the mechanic found that the BSI under the N/S dash was soaking wet. A water leak from the sunroof and blocked drains had corroded the circuit board of the BSI. He called us to see if a second hand unit will work. This is possible. There are tools that can clone one BSI into a used unit, but only if you can communicate with the original unit. True code is one such programmer with this capability.
Moral of this story: Winter is coming, make sure all drains are clear as any water leak into the vehicle can cause serious damage to wiring and modules hiding in some strange locations.