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Automatic Transmission

On-the-Road Diagnosis

The car in Figure 1 is a 2000 BMW 528i that had been to a couple of transmission shops before I got to it. The complaint was that the transmission was in failsafe mode. The car started and moved but would not upshift. The other shops also said they could not communicate with the transmission EGS module.

On-the-Road Diagnosis

Shift Pointers

Author: Rupert Sheodial

Shift Pointers

  • Author: Rupert Sheodial

The car in Figure 1 is a 2000 BMW 528i that had been to a couple of transmission shops before I got to it. The complaint was that the transmission was in failsafe mode. The car started and moved but would not upshift. The other shops also said they could not communicate with the transmission EGS module.

I hooked up my Baum CS 2000 and also found that I could not communicate with the EGS (electronic transmission control) module, but I could communicate with the DME (digital motor electronics) engine computer and I retrieved these codes:

  • 217 – CAN BUS EGS signal
  • 180 – No description
  • 118 – Throttle valve motor
  • 182 – No description
  • 193 – No description
  • 79 – Oxygen sensor bank 1
  • 19 – Vanos solenoid valve outlet
  • 215 – Oxygen sensor after cat. No signal

I immediately fired up my Dell laptop and checked my Mitchell1 software for the wiring schematic; I was lucky that I had it. I printed a copy and started checking for power supply to the computer. The schematic told me that the fuses and computer were both in the right rear of the engine compartment in the E box.

When I removed the E-box cover and checked the computer, the first thing I saw was that someone had been there before me, as there were greasy fingerprints on the computer. The fuse holder is tucked in at the back of the computer and is below; you have to physically peep in at the back to see the fuse holder and the relays.

The fuse holder can accommodate four fuses (see Figure 2). One is a spare and the other three are hot in the run position. Fuse 4, a 30-amp fuse, is the second one from the right side. This fuse was blown. I replaced the fuse, got into the car and turned the key on, and I saw the P light up on the dash and then go out. I went back to the fuse and found that it had blown again. I put another fuse in and had someone turn the ignition on, and I saw the fuse burn out.

I said to myself that this was a dead short. I started to check the wiring, and everything seemed OK. The schematic showed only one red/white wire on that circuit. In the E box I could see a lot of red/white wires, so I took a razor blade and opened up the harness and then traced the red/white wire from the fuse holder (see Figure 3). There were two #10 awg (standard wire gauge) wires with four more #14 awg wires spliced together. I then traced the four small red/white wires and found that they went to all four oxygen sensors (see Figure 4).

I unplugged the transmission harness and pulled the whole harness out to get better access to work. I did a physical examination and could not find anything wrong. The harness was so clean, there was no sign of damage or burnt wires and I still couldn’t find the short. Finally, I decided to cut out the splice and connect the wires one by one (see Figure 5). When I touched the last wire I watched the fuse burn out, then I traced it and found that all four wires in the harness had melted together but the outer insulation was like new and was never touched (see Figure 6). How this happened I don’t know.

After checking resistance on all four oxygen sensors and getting the same reading, I concluded that all the oxygen sensors were good. I ran four new wires to the oxygen sensors, and that solved the problem. After I repaired the wiring I hooked up my Baum CS 2000 and retrieved two codes, gear monitoring and 146 – no description. I cleared all the codes and everything was perfect.

Rupert Sheodial is president of Bigappplemobile Automotive Diagnostics, Jamaica, N.Y., and formerly operated Veronica Transmissions in New York City.

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