DTC 46, Idle Speed Control Motor Circuit: Notes

Idle Speed Control (ISC) motor opens and closes the throttle valve according to signals from ECM. When a condition occurs requiring a higher idle speed, ECM will send a signal to ISC motor which will extend the plunger of the ISC motor, which opens the throttle plates to increase idle speed. ECM will reverse the polarity to ISC motor causing throttle plates to close, thus decreasing idle speed when the higher idle speed is no longer necessary. DTC 46 will set when the following conditions are met:

• If battery voltage is greater than 12 volts, idle switch is closed and the change in throttle valve opening is less than .3 degrees after ECM has energized the ISC motor for more than 8 milliseconds.
• If throttle valve opening is sensed at less than 2.5 degrees.
• If ISC motor drive voltage is sensed twice when the signal is not fed from ECM.
• If throttle valve opening is not within 3 degrees of the target throttle valve opening under any of the following conditions:
  1. 1) Battery voltage is greater than 12 volts.
  2. 2) Idle switch is closed.
  3. 3) 3 seconds since engine was started.
  4. 4) During deceleration or fast idle.
  5. 5) Electrical load, A/C or transaxle Drive range idle-up signal not input to ECM.

1. Checks electrical load idle-up circuit.
2. Checks for an open in White/Blue wire.
3. Checks for an open in Gray/Black wire or for a faulty ISC motor relay.
4. Checks for an open, short to ground or short to voltage in Gray/Red, Gray or Gray/Yellow wires, or for a faulty ISC motor.
5. Checks for an open, a short to ground or a short to voltage in Gray/Red, Gray or Gray/Yellow wires, or for a faulty ISC motor.
6. Checks for an open in Black/Blue wire.
7. Checks for an open, a short to ground or a short to voltage in Light Green wire, or for a faulty ECM.
8. Checks for a short to voltage in Gray/Green wire, or for a faulty ISC motor.
9. Checks for an open, a short to ground or a short to voltage in Gray/Green wire, or a faulty ISC motor or ECM.