Diagnostic Aids

The coolant temperature sensor, in rare cases, may fail to indicate the correct coolant temperature without setting a malfunction code (Code 14 or 15). This could result in turning on the hot light without having an overheating condition. It could also result in engine overheating without turning on the hot light. Check coolant sensor temperature-to-resistance values in SENSOR RANGE CHARTS article.

Monitor the voltage of each terminal while moving related harness connectors, including control module harness. If the fault is induced, the voltage will change. This may help locate intermittent problems. If code reappears with no apparent problems, replace control module.

Fig 1: Code 26 Troubleshooting Flowchart 2 Of 3 (3.8L H Body)

Courtesy of GENERAL MOTORS CORP.

This determines if the problem is the circuit or the component. Factory-installing ECM has an internal fuse and it's unlikely ECM needs replacing.

Fig 2: Code 26 Troubleshooting Flowchart 3 Of 3 (3.8L H Body)

Courtesy of GENERAL MOTORS CORP.