Volvo produced a bulletin (Number 83-84) regarding a water leak from the sunroof. The root cause and repair provided in this bulletin is informative and well done. What it doesn’t cover is where the water travels to. And that may be partly due to the fact that water takes the path of least resistance. It may not travel in the same direction with every car. Mike Abrey from Franks Transmission Inc. had a 2004 XC90 come in to the shop with several codes logged in the system.
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An ECM-400C code for a fault detected in the leak diagnostic unit, an ECM-530B for a communication fault between the ECM and the TCM and an ECM-928C for a fault in the steering wheel module or CAN communication. What a can of worms this could be. Where do you start? Especially if you are unaware of that a leaking sunroof exists along with no evidence or clues to point you in that direction. Mike opted to check fuses and connectors which was a clever place to begin.
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What he discovered was this sunroof water leak worked its way down the door pillar, across some lines and into the Central Electronic Module which is a box containing 14 relays (Figure 1). When he started pulling out the relays each and every one of them were contaminated (Figure 2). Fixing the leak, changing the CEM and programming, the vehicle was safe for sailing, I mean driving.
