DTC 23

Code 23 Diagnostic Chart:

Code 23 Circuit Diagram:

CIRCUIT DESCRIPTION:

Code 23 indicates that the ECM has monitored the voltage at ECM terminal "21" and that it remains low, instead of rising and falling as the M/C solenoid is turned "ON" and "OFF." This could be caused by an open in the M/C solenoid circuit or a ground on the ECM side of the M/C solenoid. An open would cause a full rich condition, poor fuel economy, exhaust odor, smoky exhaust, and possibly, poor driveability. A ground would cause a full lean condition and poor driveability.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks for a complete circuit from the battery through the M/C solenoid dwell lead. Voltage here should be battery voltage. A zero voltage reading could be caused either by an open between the dwell connector and ignition source or a ground on the ECM side of the M/C solenoid.

2. Checks for B+ on CKT 439 to the ignition source. The test light should light between the ignition source and ground.

3. This step determines whether the fault is in the M/C solenoid, a grounded CKT 411 to the ECM, or the ECM. A light would indicate a grounded CKT 411 to terminal "21," or a faulty ECM. A voltmeter can't be used because it is normal to have enough current flow through the ECM, even with the circuit open, to make a voltmeter read, but not enough to light a test light.

4. This checks for grounded CKT 411 to ECM Terminal "21." If it is grounded, the light will stay "ON."

5. Checks for an open CKT 411 from the solenoid to ECM. A normal circuit would read approximately battery voltage at the ECM Terminal "21."

6. A normal solenoid has about 20 to 32 ohms of resistance. The ECM does not have to be replaced if the M/C solenoid resistance is under 10 ohms. The ECM is equipped with a fault-protected quad driver, so replace the M/C solenoid only.