DTC 41

DTC 41 Chart Ignition Control Circuit:

Ignition System Wiring Diagram:

Circuit Description:

The ignition system provides two timing inputs to the ECM, high resolution (360 pulses per crankshaft revolution) and low resolution (4 pulses per crankshaft revolution). The ECM uses these two reference pulses to determine individual ignition spark timing for each cylinder.

Once the ECM calculates ignition timing, the timing signal will be sent to the ignition coil module on the IC circuit. Each timing pulse received by the ignition coil module, on the IC circuit, will trigger the ignition coil module to operate the ignition coil. Secondary ignition voltage is induced and is then sent to the distributor for distribution to each spark plug.

The IC signal voltage ranges from about 0.5 volt to 4.5 volts.

If a DTC 41 is detected, the ECM will disable the fuel injectors to prevent flooding of the engine. DTC 41 will set if the IC circuit problem occurs during cranking.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 41 will set if:

^ Voltage on CKT 423 exceeds 4.6 volts.
^ Engine speed is less than 1500 RPM.

2. Without the engine running or cranking there would be no voltage present on the IC line.

3. This check determines if the IC signal from the ECM is available at the ignition coil module. The IC circuit voltage should be between about 0.5 and 4.5 volts.

4. The remaining tests begin to check that the ignition coil module circuitry is OK.

5. If all wiring and connections are OK, check the ignition coil or the ignition coil voltage supply.

Diagnostic Aids:

Since the ignition coil module gets its power from the coil, check the ignition feed circuit to the ignition coil for opens.