Shift Pointers
- Author: Jesse Zacarias
- Subject Matter: Diagnosis
- Vehicle Application: 2003 Volkswagen Passat
- Issue: Water damage to TCM
A 2003 Volkswagen Passat come into our shop with multiple codes and harsh engagements and was in failsafe mode. The customer said he parked the vehicle and when he started it the next day he noticed the problem. At times the TCM would fail to communicate with the scan tool. When we removed the carpet at the passenger-side floorboard to check the TCM for voltage, we noticed the whole bottom of the floor had about 2 inches of water (Figure 1).
When we opened up the box to access the TCM we noticed the box full of water (Figure 2), and when we looked inside the TCM we knew it was damaged (Figure 3).
Before we replaced the TCM we needed to find out the reason for the water at the floorboard; otherwise our new TCM would be destined for a short life. It was then when we noticed that the battery had been replaced, the water deflector at the bottom of the windshield was damaged and the cover plate was not inserted properly into the water deflector right above the cabin-air filter (figures 4 & 5). This allowed the water to run down the water deflector, thru the cover plate and into the cabin air filter, ending up on the passenger-side floorboard were the TCM is situated.
We ordered a new water deflector, cover plate and cabin air filter at a total cost of about $100. One thing to mention here is, when you replace the water deflector do not try to install it by bending it as this will cause it to break. (Ask me how I know.) It is best to remove the bolts from the hood and just move the hood forward and install the water deflector through the top (Figure 6).
When installing the cover plate, make sure to insert it into the water-deflector slot, especially above the cabin-air filter (Figure 7).
This kind of mistake will not show up right away, unless it is done during the rainy season. In this particular case the battery was replaced months ago, but as soon as we got the first rains the problem showed up.
One more thing to think about next time we replace a battery.
Jesse Zacarias is the owner of Elec-Tran Diagnostics (www.electrandiagnostics.com) in Gilroy, Calif., and part of the research-and-development department at Valve Body Pros.
