Grand Caravan suffers from puzzling battery drain after liftgate repair.

A 2012 Dodge Grand Caravan gave us fits after what should have been a simple repair. Originally, this vehicle was brought to us from another shop with a complaint of the rear power liftgate not working. Upon initial inspection, we found that the rear liftgate module and connector were badly corroded. We called for a new module and wiring repairs to the connector. These repairs were carried out by the shop that sent us the vehicle. Once repaired, the liftgate returned to normal operation.

A new problem

About a week later we gat a call from the same shop and now we had a complaint that there was a draw on the battery and that the battery would go dead overnight. The shop also noted that the draw would go away if the rear liftgate was opened.

We brough the vehicle to our facility and did the usual, scanned it for codes, checked to see how big the draw was and so forth. There were no codes stored, the tailgate operated normally, and we measured a 2.2 amp draw only when the liftgate was closed. As soon as the liftgate was opened, the draw went to less than 100 mA (milliampere). Obviously, there was some connection between the tailgate and the draw.

Limit switch

When we looked at the system, there is a limit switch that tells the module when the liftgate is open. We accessed the switch and sure enough the draw and the switch state mirrored each other. When the switch was activated by opening the liftgate the draw stopped. Our initial though was that the liftgate module was being confused by the switch, however with a 2.2 amp draw it had to be more than just a single module waking up.

The liftgate module is on the Body CAN BUS so we decided to take a look at the BUS. The thinking here is that if the CAN BUS was active, then the Body BUS was live. This would account for the heavy draw. Fig 1 shows the state of the CAN BUS while opening and closing the liftgate. As you can see, the BUS goes from no activity to full activity as the liftgate is opened and closed. It looks as if the liftgate module is waking up the entire Body BUS and the BUS is going to sleep when the module turns off. Based on this analysis, the module is working back to front. The module should wake up when the gate is opened and go to sleep when the gate is closed, not the other way around. Time to take a closer look at the liftgate module and wiring.

Less than ideal

The module was pulled out, and the wiring was inspected, we found that the wiring repair to the connector was less than ideal. It appeared that instead of replacing the connector with the damaged pins, the shop enlarged the holes the damaged pins were in and shoved pins that would fit into the connector. Obviously, the repaired wiring cannot be verified to be making a proper connection. We found the proper pins, rewired the connector and retested the vehicle. Everything performed normally, and the battery draw was eliminated.

The moral of the story: If you are going to the trouble of repairing connectors, make sure you do it properly.