Diagnostic Aids
When attempting to diagnose an intermittent problem, use scan tester to review supplemental diagnostic information. Supplemental data (scan tester MALF HISTORY) can be used to help duplicate an intermittent problem. Using Diagnostic Service Probe (12092782) allows voltage to be read on wires without disconnecting connectors. Speedometer will not work if VSS has failed. If VSS reading is accurate and speedometer is incorrect, diagnose speedometer using appropriate service manual. Ensure VSS resistance is 700-900 ohms. When code is set, PCM will substitute a default value based upon RPM.