DTC 46

CODE 46 IDLE SPEED CONTROL (ISC) MOTOR CIRCUIT (WITH UPGRADED EMISSIONS ONLY)

Diagnostic Chart: 1 Of 3:

Diagnostic Chart: 2 Of 3:

Diagnostic Chart: 3 Of 3:

Idle Speed Control Wiring Schematic:

CIRCUIT DESCRIPTION
The Idle Speed Control (ISC) motor opens and closes the throttle valve according to signals from the Engine Control Module (ECM). When a condition arises which demands a higher idle speed, the ECM will send a signal to the ISC motor which will extend the plunger of the ISC motor, thus opening the throttle plates to increase the idle speed. When the higher idle speed is no longer needed, the ECM will reverse the polarity to the ISC motor which will cause the throttle plates to close, thus decreasing the idle speed.

Diagnostic Trouble Code (DTC) 46 will set if the following conditions are met:
^ If battery voltage is greater than 12 volts, the idle switch is closed and the change in throttle valve opening is less than 0.3 degrees after the ECM has energized the ISC motor for more than 8 milliseconds.
^ If the throttle valve opening is sensed at less than 2.5 degrees.
^ If the ISC motor drive voltage is sensed twice when the signal is not fed from the ECM.
^ If the throttle valve opening is not within 3 degrees of the target throttle valve opening under any of the following conditions:

1. Battery voltage is greater than 12 volts.
2. The idle switch is closed.
3. 3 seconds since the engine was started.
4. During deceleration or idle.
5. Electrical load, A/C or transaxle "D" range idle-up signal not inputted to the ECM.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
(Part 1 of 3)
1. This checks the electrical load idle-up circuit.
2. This checks for an open in WHT/BLU wire.
3. This checks for an open in GRA/BLK wire or for a faulty ISC motor relay.
4. This checks for an open, a short to ground or a short to voltage in GRN/RED, GRA or GRA/YEL wires or for a faulty ISC motor.
(Part 2 of 3)
5. This checks for an open, a short to ground or a short to voltage in GRN/RED, GRA or GRA/YEL wires or for a faulty ISC motor.
6. This checks for an open in BLK/GRN wire.
7. This checks for an open, a short to ground or a short to voltage in LT GRN wire or for a faulty ECM.
(Part 3 of 3)
8. This checks for a short to voltage in LT GRN/YEL wire or for a faulty ISC motor.
9. This checks for an open, a short to ground or a short to voltage in LT GRN/YEL wire, a faulty ISC motor or for a faulty ECM.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect ECM connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

DTC 21, DTC 22 and DTC 46 stored at the same time could be the result of an open LT GRN wire.