How to Check Transmission (TCU) Error Codes

Author: FSM

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The "Power" light indicates transmission codes. Long blinks = 10, short blinks = 1. In other words, two long and two short blinks is a code 22. One long and one short is code 11. The following self diagnosis will show any fault codes for the transmission.

The most common trouble code is "11" and is almost always caused by a faulty transmission resistor located between the battery and fender.

To perform the self diagnosis test for EXISTING problems:

  1. Warm up engine by driving at speeds greater than 12mph.
  2. Stop vehicle and turn ignition switch OFF.
  3. Turn ignition switch ON and make sure POWER indicator lamp comes on.
  4. Turn ignition switch OFF.
  5. Move selector lever to D and turn manual switch ON.
  6. Turn ignition switch ON.
  7. Move selector lever to "3" and turn manual switch OFF.
  8. Move selector level to "2" and turn manual switch ON.
  9. Move selector lever to "1" and turn manual switch OFF.
  10. Partially depress accelerator pedal (to turn idle switch off).
  11. Check code as displayed on POWER light. Blinking once every 1/4sec is normal.

To perform the self diagnosis test for PREVIOUS problems:

  1. Warm up engine by driving at speeds greater than 12mph.
  2. Stop vehicle and turn ignition switch OFF.
  3. Turn ignition switch ON and make sure POWER indicator lamp comes on.
  4. Turn ignition switch OFF.
  5. Move selector lever to "1" and turn manual switch ON.
  6. Turn ignition switch ON.
  7. Move selector lever to "2" and turn manual switch OFF.
  8. Move selector lever to "3" and turn manual switch ON.
  9. Move selector lever to "D" and turn manual switch OFF.
  10. Partially depress accelerator pedal (to turn idle switch off).
  11. Check code as displayed on POWER light. Blinking once every 1/4sec is normal.

List of TCU Trouble Codes

Trouble Code Item
11 Duty solenoid A
12 Duty solenoid B
13 Shift solenoid 3
14 Shift solenoid 2
15 Shift solenoid 1
21 ATF temp sensor
22 Atmospheric sensor
23 Engine revolution signal
24 Duty solenoid C
31 Throttle sensor
32 Vehicle speed sensor 1
33 Vehicle speed sensor 2

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