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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.



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

Fig 1: Code 26 Troubleshooting Flowchart 2 Of 3 (3.8L C & E Body)
G91H07316Courtesy of GENERAL MOTORS CORP.
  1. This determines if the problem is the circuit or the component. Factory-installed PCM has an internal fuse and it's unlikely PCM needs replacing.
Fig 2: Code 26 Troubleshooting Flowchart 3 Of 3 (3.8L C & E Body)
G91J07317Courtesy of GENERAL MOTORS CORP.
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