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DTC P1597: Speed Control Switch Always Low

NOTE: For connector terminal ID, see CONNECTOR IDENTIFICATION  . For wiring diagram, see WIRING DIAGRAMS article.
NOTE: Speed control switch is monitored when ignition is on and battery voltage is more than 10.4 volts. DTC may be stored in Powertrain Control Module (PCM) if speed control on/off switch circuit voltage is less than .39 volts for 2 minutes. Possible causes are: defective clockspring, defective speed control on/off or resume/accel switch, defective PCM, or defective connectors or wiring.
  1. Turn ignition on with engine off. Using scan tool in SENSORS mode, read speed control switch voltage. Speed control switch voltage may also be referred to as S/C 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, go to step  7 .
  2. Turn ignition off. Disconnect speed control on/off switch 2-pin connector at rear of speed control on/off switch assembly on steering wheel. Turn ignition on with engine off. Using scan tool in SENSORS mode, read speed control switch voltage. If speed control switch voltage does not change to 5 volts, go to next step. If speed control switch voltage changes to 5 volts, replace speed control on/off switch. Perform TEST VER-4  .
  3. Turn ignition off. Disconnect speed control resume/accel switch 2-pin connector at rear of speed control resume/accel switch assembly on steering wheel. Turn ignition on with engine off. Using scan tool in SENSORS mode, read speed control switch voltage. If speed control switch voltage does not change to more than 4 volts, go to next step. If speed control switch voltage changes to more than 4 volts, replace speed control resume/accel switch. Perform TEST VER-4  .
  4. Turn ignition off. Disconnect clockspring connector No. 1. Clockspring connector No. 1 is a 5-pin connector located near steering wheel. See Figure . Turn ignition on with engine off. Using scan tool in SENSORS mode, read speed control switch voltage. If speed control switch voltage does not change to 5 volts, go to next step. If speed control switch voltage changes to 5 volts, replace clockspring. Perform TEST VER-4  .
  5. Turn ignition off. Ensure speed control on/off switch 2-pin connector at rear of speed control on/off switch assembly on steering wheel is still disconnected. Reinstall clockspring connector No. 1. Disconnect PCM connectors. PCM is located at passenger's side front corner of engine compartment on inner fender panel. Using ohmmeter, check resistance between both terminals on speed control on/off switch 2-pin connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair Red/Light Green wire and Black/Light Blue wire between PCM and speed control on/off as they are shorted together. Perform TEST VER-4  .
  6. Ensure speed control on/off switch 2-pin connector at rear of speed control on/off switch assembly and PCM connectors are still disconnected. Using ohmmeter, check resistance between ground and terminal No. 32 (Red/Light Green wire) on PCM connector C3. If resistance is 5 ohms or more, replace PCM. Perform TEST VER-4  . If resistance is less than 5 ohms, repair short to ground on Red/Light Green wire between PCM and speed control on/off switch assembly. Perform TEST VER-4  .
  7. Inspect wiring harness and connectors between speed control on/off switch, speed control resume/accel switch, clockspring and PCM. Clockspring is located on steering column, below steering wheel. PCM is located at passenger's side front corner of engine compartment on inner fender panel. If necessary to check connector C200, this is a Black 42-pin connector located behind driver's side of instrument panel, near kick panel. See Figure . If no problem exist, test is complete. If any problems exist, repair wiring or connectors as necessary. Perform TEST VER-4  .
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