DTC P1597: Speed Control Switch Always Low: Testing
- Turn ignition on. Using scan tool, record all DTCs and freeze frame data. Erase DTCs. Using scan tool, observe speed control switch voltage. If speed control switch voltage is less than one volt, go to next step. If speed control switch voltage is one volt or more, test is complete.
- Turn ignition off. Disconnect speed control switch 2-pin harness connector. Measure resistance between speed control switch signal circuit (Pink/Light Green wire) and speed control switch ground circuit (Black/Tan wire) at speed control switch harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short between speed control switch signal circuit and speed control switch ground circuit. Speed control switch signal circuit runs from speed control switch through clockspring to powertrain control module. Speed control switch ground circuit runs from speed control switch through clockspring to body control module.
- Turn ignition on. Using scan tool, observe speed control switch voltage. If speed control switch voltage is not 5 volts, go to next step. If speed control switch voltage is 5 volts, replace speed control switch.
- Turn ignition off. Disconnect Powertrain Control Module (PCM) harness connectors. PCM is located to left of Power Distribution Center (PDC) in engine compartment, next to air cleaner. Inspect harness connector and clean/repair as necessary. Measure resistance between ground and terminal No. 41 (Red/Light Green wire) at PCM harness connector C2. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in speed control signal circuit between speed control switch, clockspring and PCM.
- If no other potential causes are remaining, replace PCM. After replacing PCM, PCM MUST be reprogrammed. See POWERTRAIN CONTROL MODULE under PROGRAMMING.