DTC P1597: Speed Control Switch Always Low
- Turn ignition on with engine off. Using scan tool, read speed control switch voltage. If voltage is less than one volt, go to next step. If voltage is one volt or more, go to step 8.
- Turn ignition off. Disconnect speed control ON/OFF/SET switch 2-pin connector. Turn ignition on with engine off. Observe scan tool voltage reading. If voltage did not change to 5 volts, go to next step. If voltage changed to 5 volts, replace speed control ON/OFF/SET switch. See SPEED CONTROL SWITCHES under REMOVAL & INSTALLATION. Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
- Turn ignition off. Disconnect speed control RESUME/ACCEL switch. Turn ignition on with engine off. Observe scan tool voltage reading. If voltage did not change to 5 volts, go to next step. If voltage changed to 5 volts, replace speed control RESUME/ACCEL switch. See SPEED CONTROL SWITCHES under REMOVAL & INSTALLATION. Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
- Disconnect clockspring 5-pin connector located on steering column. See Figure. If voltage did not change to 5 volts, go to next step. If voltage changed to 5 volts, replace clockspring. See
AIR BAG RESTRAINT SYSTEMS - CARS article. Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
- Turn ignition off. Disconnect PCM connectors. Using a DVOM, check resistance between speed control ON/OFF/SET switch 2-pin connector terminals. See WIRING DIAGRAMS . If resistance is greater than 5 ohms, go to next step. If resistance is less than 5 ohms, repair short between Black/Light Blue wire (sensor ground) and Red/Light Green wire (speed control switch signal). Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
- Using a DVOM, check resistance between speed control ON/OFF/SET switch 2-pin connector signal circuit terminal and ground. If resistance is greater than 5 ohms, go to next step. If resistance is less than 5 ohms, repair short to ground in Red/Light Green wire between PCM and speed control ON/OFF/SET switch. Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
- If no other possible causes are found, replace PCM. Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
- Turn ignition off. Inspect connectors and wiring for PCM, speed control servo, clockspring and speed control switches. If no faulty connections or circuits are found, go to next step. If faulty connectors or circuits are found, clean or repair as necessary. Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
- Monitor speed control switch voltage on scan tool. Disconnect speed control ON/OFF/SET switch 2-pin connector. If voltage did not change from less than 4 volts to greater than 4 volts, go to next step. If voltage changed from less than 4 volts to greater than 4 volts, replace speed control ON/OFF/SET switch. See SPEED CONTROL SWITCHES under REMOVAL & INSTALLATION. Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
- Disconnect speed control RESUME/ACCEL switch. If voltage did not change from less than 4 volts to greater than 4 volts, go to next step. If voltage changed from less than 4 volts to greater than 4 volts, replace speed control RESUME/ACCEL switch. See SPEED CONTROL SWITCHES under REMOVAL & INSTALLATION. Perform POWERTRAIN VERIFICATION TEST VER-4 under VERIFICATION TESTS.
Courtesy of DAIMLERCHRYSLER CORP.