Copyright © 1998 General Motors Corp. 6–107
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
Main code 62 indicates the retarder temperature sensor or circuitry is providing a signal outside the usable range of
the ECU. Main code 62 can be the result of a hardware failure or an actual extremely high or low temperature
condition.
NOTE: A combination of codes 62 23, 33 23, and 21 23 indicates a problem with one of the branches of the
common ground wire (wire 135) between the throttle and temperature sensors.
Active Indicator Clearing Procedure:
• Power down
• Manual
• Self-clearing
NOTE: Before troubleshooting, read Pages 6–17 and 6–18 of Section 6–5. Also, check the transmission
fluid level.
Troubleshooting:
1. Check the retarder temperature with a DDR. If a DDR is not available, use the shift selector
display to determine if the code is active (cycle the ignition on and off at least once since the code
was logged to clear the active indicator). If a condition that is unreasonable for the current
conditions exists, go to Step 3.
2. If Step 1 reveals that the extreme temperature indication is no longer present, the temperature limit
could have been reached due to operational or ambient temperature extremes. Proceed cautiously,
it is unlikely there is a sensor hardware fault.
3. Remove the connector at the ECU. Measure resistance between B1 and B4. Compare resistance
value to chart (see Figure 6–35) to see if reading is within expected operating range.
4. Disconnect the sensor connector and remove the connector at the ECU. Check the sensor and the
ECU terminals for dirt, corrosion, and damage. Clean or replace as necessary (refer to Appendix
E).
5. Check the temperature sensor circuit for opens (Code 62 23), shorts between wires, and short-to-
ground (Code 62 12). If a wiring problem is found, isolate and repair. See Appendix E for
connector service information.
6. If no wiring problem is found, replace the retarder temperature sensor (refer to transmission
Service Manual for proper procedure).
7. If the problem recurs, run spare wires for the retarder temperature circuit. See Appendix D for
location of spare wires and Appendix E for connector service information.
8. If the condition continues to recur, replace the ECU. If replacing the ECU corrects the problem,
reinstall the original (bad) ECU to confirm that the problem is in the ECU. If the original ECU now
works, inspect the ECU connectors for any corrosion or damage which may cause an intermittent
condition. If the original problem recurs, reinstall the replacement ECU.
Main
Code
Subcode Meaning
62 12 Retarder temperature sensor failed low (–45°C; –49°F)
62 23 Retarder temperature sensor failed high (178°C; 352°F)
CODE 62 XX — RETARDER TEMPERATURE SENSOR (Figures 6–36, 6–37)
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