Powertrain Controls - ECM/PCM

DTC 41 Chart:

Ignition System Circuit:

CIRCUIT DESCRIPTION
During cranking the Ignition Control (IC) module monitors the crankshaft position sensor "A" and "B" signals. The signals are used to determine the correct cylinder pair to spark first. After the signals have been processed by the IC module, it sends a fuel control reference pulse to the PCM. When the PCM receives this pulse it will command all eight injectors to open for one priming shot of fuel in all cylinders. After the priming, the injectors are left "OFF" for the next eight fuel control reference pulses from the IC module (two crankshaft revolutions). This allows each cylinder a chance to use the fuel from the priming shot. During this waiting period, a cam pulse will have been received by the PCM. Now the PCM begins to operate the injectors sequentially based on true camshaft position.

DTC 4I WILL SET WHEN
- DTC 12 not set.
- Cam reference pulse not received for 5.3 seconds.
- 4X reference pulses being received.
- Engine speed 1600 RPM or less.

ACTION TAKEN (PCM WILL DEFAULT TO)
With a current DTC 41 set, the PCM will illuminate the Malfunction Indicator Lamp (MIL) (Service Engine Soon).

DTC 41 WILL CLEAR WHEN
The fault no longer exists.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Check to see if DTC 35 is set because a REF LO problem can cause other ignition problems.
2. Checking the resistance of the camshaft position sensor. The resistance should be 800-2100 ohms. If the resistance is greater, check for an open or if it is less, check for a short to ground or each other.
3. Checking if CKT 632 or CKT 633 is shorted to ground.
4. If the sensor is able to produce a DC voltage greater than 0.2 volt the sensor is OK.
5. With engine running, measuring greater than 4 Hertz shows that the ignition control module is producing CAM pulses.
6. Checking for a circuit fault or faulty IC module.

DIAGNOSTIC AIDS
An intermittent can be caused by a poor connection, bared or broke wires.