The following ONLY occurs during wet weather:
I have a 92 Honda Accord LX with automatic transmission. Starting from a stop, the car feels as though it’s trying to start in third gear. Once we get going, I cannot seem to get it to go beyond third gear. On the highway, I can’t go past 50 mph, and the tachometer stays around 3. I noticed that with the engine running and while at a stop, if I shift into other gears, the D4 light on the dashboard remains lit (i.e., if I shift to reverse, the R light and D4 light are lit). The car moves in the correct direction while in the other gears, but the D4 light stays on.
I think the Transmission Control Module (TCM) is bad, but I wanted to get others’ opinions. Is there a way I can test if the TCM is bad? Do you have any other ideas of the problem?
Would anyone know how I can read technical service bulletin SN920701 (dated 07/01/1992) to know how to identify the problem with my Accord? Thanks!
I applaud your desire to read the technical bulletin. You probably also need to get up to speed on computer operated Honda transmissions. When you do that email me back about where you found the information.
You likely have a problem with one of the sensors that the TCM needs to determine the shift points. If this were my car, I would be looking and the Vehicle Speed Sensor, VSS. The TCM definitely needs this to determine the shift points. But it also could be the Throttle Position Sensor, TPS, the MAP sensor, or the turbine input shaft speed sensor as these are used in calculating the shift points. The TCM will default to ‘limp home’ mode when it detects a critical fault. The default mode is lock in third gear forward, full line pressure, and set the OD light.
Unless you enjoy doing this sort of troubleshooting, have the test equipment, and the transmission service manual, you should take the car to a transmission shop capable in Honda transmission and have the technician scan the computer for Diagnostic Trouble Codes, DTCs. The problem might be just a wiring problem or a defective sensor.
Hope I have helped.
Please post back with the continuation of this saga.
I did a little research on Alldata about this car. The transmission computer is separate from the ECM – a TCM box right next to the ECM box. The transmission has NM and NC sensors – main shaft RPM sensor and counter shaft RPM sensor. I didn’t find a separate VSS to run the ECM and speedometer.
I gather from a description that the TCM codes are accessed by jumpering the pins for the ECM code readouts and reading the flashes of the OD light. The DTCs were Honda proprietary single and double digits.
Research on Alldata to get additional information.