Code 46, 47

IDLE SPEED CONTROL VALVE COIL 1 DRIVE CIRCUIT - DTC 46
IDLE SPEED CONTROL VALVE COIL 1 DRIVE CIRCUIT - DTC 47

The ECM looks for the idle speed control valve coil drive voltage outside the normal range for valve operation.

The idle speed actuator is a stepper motor that adjusts the flow of air bypassing the throttle valve to control idle speed. The ECM drives the idle speed actuator toward open or close by pulsing coil 1 and coil 2. The coil pulses are phased 9O° apart. To reverse the valve direction (e.g. from opening to closing), the phasing is reversed. The idle speed control valve signal can he monitored with an oscilloscope. Loss of one coil will cause the stepper motor to he inoperative.

Stepper Motor Drive Signal:

The ECM will flag DTC 46 or 47 if the drive circuit voltage is less than 0.85 volt when OFF or less than 12.25 volts when ON.

Conditions Required For DTC 46 Flagging
Ignition - ON.
Coil 1 circuit voltage OFF - Less than 0.85 volt.
Coil 1 circuit voltage ON - Less than 12.25 volts.
Response time - 100 milliseconds.

Condition Required For DTC 47 Flagging
Ignition - ON.
Coil 2 circuit voltage OFF - Less than 0.85 volt.
Coil 2 circuit voltage ON - Less than 12.25 volts.
Response time - 100 milliseconds.

Limp Home Default
None

Possible Faults
- Low battery voltage.
- Poor ECM power feed or ground connections.
- Open or short circuit in coil 1 or coil 2 drive circuit wiring.
- Open or short circuit in coil 1 or coil 2 ground circuit wiring.
- Water ingress to ECM connector.
- Defective idle speed actuator.

Diagnostic Notes
1. DTC 46 applies only to coil 1 (idle speed control valve pins 1 and 4).
DTC 47 applies only to coil 2 (idle speed control valve pins 2 and 3).

2. The idle speed control valve coil resistance should be 40-60 ohms.
3. Drive the idle speed control valve by switching OFF the ignition, waiting 10 seconds, then switching ON the ignition.

Circuit Diagram

Circuit Diagram:

Flow Chart - DTC 46, 47

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Flow Chart - DTC 46, 47: