Copyright © 1998 General Motors Corp. 6–41
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
Main code 24 indicates the ECU has detected either a high or low fluid temperature in the transmission sump (via
the sump temperature sensor in the internal harness). All shifts are inhibited when Code 24 12 is set (only Neutral
range operation is allowed). No upshifts are allowed above a calibration range when Code 24 23 is set. All inhibits
are cleared when the temperature conditions are normal. A related code is 33 12 which indicates a temperature
reading outside the usable range of the sensor and indicates a probable sensor failure.
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 ECU input voltage.
Troubleshooting:
A. Code 24 12:
1. If Code 24 12 is set and the outside temperature is low enough to cause this trouble, lower than
–32°C (–25°F), the ECU will not allow range operation (See Table 6–4 on next page). The sump
must be preheated to an acceptable temperature to avoid logging codes and transmission
diagnostic response.
NOTE: Medium cold fluid, –29°C (–20°F) to –7°C (+20°F), will allow reverse, neutral, and second-range-start
operation. Only hold override upshifts are allowed.
2. If ambient temperature does not match the sump temperature reading (check using diagnostic
tool), compare resistance versus sump fluid temperature (refer to Figure 6–12). Then check the
sensor wiring for opens, shorts, or shorts-to-ground.
3. If the sensor wiring is satisfactory, drain the fluid, remove the control module, and replace the
temperature sensor (refer to appropriate transmission Service Manual).
4. If the condition persists, 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 that may cause an intermittent condition.
If the original problem recurs, reinstall the replacement ECU.
Main
Code
Subcode Meaning
24 12 Oil temperature cold
24 23 Oil temperature hot
CODE 24 XX — SUMP FLUID TEMPERATURE (Figures 6–10, 6–11)
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