P0351

DTC P0351

CIRCUIT DESCRIPTION
DTCs P0351 through P0354 Ignition Coil Primary/Secondary Feedback Circuit diagnostic monitors the primary circuitry of individual ignition coils for the successful completion of an ignition event. The ignition trigger signal and ignition fail-safe input signal provide crucial information in the control of ignition system timing and the activation of the fail-safe function. Based on the initial timing angle, calculated from the crankshaft and the camshaft position signals, the powertrain control module (PCM) calculates the ignition trigger signal. The ignition trigger signal is then sent to the ignition control circuitry located in each ignition coil. The ignition control circuitry initiates the ignition dwell period by commanding the power transistor ON. When the PCM determines the proper time to provide spark, the PCM turns OFF the ignition trigger signal. In response to the PCM signal, the ignition coil control circuitry turns OFF the power transistor, producing a high voltage discharge from the secondary coil windings. After the spark has occurred, the control circuitry sends an ignition fail-safe input signal back to the PCM, confirming that an ignition event has taken place. If the ignition fail-safe input signal is not received by the PCM, a cylinder specific DTC will set.

Anytime the fail-safe input signal is lost, engine operation will enter the fail-safe function. If engine load exceeds certain parameters during the fail-safe function, Fuel Cut-off mode is activated and fuel injector operation is ceased. The suspension of fuel injection in the Fuel Cut-off mode protects the catalytic converter from damage. Damage can occur when excess unburned fuel reaches the converter and causes the catalyst to overheat.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC P0351 Ignition Coil 1 Control Circuit
- DTC P0352 Ignition Coil 2 Control Circuit
- DTC P0353 Ignition Coil 3 Control Circuit
- DTC P0354 Ignition Coil 4 Control Circuit

CONDITIONS FOR RUNNING THE DTC
- The engine is running.
- DTC P0351, P0352, P0353, and P0354 run continuously once the above condition has been met.

CONDITIONS FOR SETTING THE DTC
No ignition coil fail-safe input signal to the PCM for 2 consecutive ignition trigger signal cycles, when the engine is cranking or running.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL).
- The PCM stores the conditions that were present when the DTC set as Freeze Frame data.
- The PCM enters the fail-safe function and begins Fuel Cut-off mode operation during high engine load operation.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- The DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
- A DTC can be cleared by using the scan tool Clear DTC Information function.

DIAGNOSTIC AIDS
- Check for the following conditions:
- An interruption of the ground circuit or voltage supply to the ignition coil will prevent a proper ignition event from taking place. A DTC P0351 through P0354 will set if there is a fault in any of the ignition coil circuits.
- If DTCs P0352, P0353, and P0354 are present, the fault is located in the shared electrical circuits or shared components of the ignition coils.
- Inspect the ignition coil grounds at G 105 for a clean and tight connection.
- If no engine misfire is felt when the DTC sets, inspect for a fault in the Ignition Fail-Safe Input circuit.
- Inspect the noise filter for an internal short or low resistance. The ignition coil may not receive adequate voltage during high load conditions if the noise filter is faulty. A good noise filter will indicate infinite resistance (OL) with a DMM after the capacitor inside the filter is charged up.
- Unless the ignition key is cycled or the DTCs are cleared, the PCM waits to receive ignition fail-safe signals before providing fuel injector operation.
- An intermittent malfunction may be caused by a fault in the ignition coil electrical circuit. Inspect the wiring harness and the components for an intermittent condition.
- Repair any electrical circuit faults that were found.
- The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

TEST DESCRIPTION

Step 1 - Step 11:

Step 12 - Step 19:

The numbers below refer to the step numbers in the diagnostic table.
1. The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. If DTCs P0351, P0352 P0353, and P0354 are present, the fault is located in the shared electrical circuits or shared components of the ignition coils.
3. If there is no engine misfire present, there is a fault in the Ignition Fail-Safe Input signal circuit.
4. DTC P0351 indicates a failure in the circuits of ignition coil 1. DTC P0352 indicates a fault with ignition coil 2. DTC P0353 indicates a fault with ignition coil 3. DTC P0354 indicates a fault with ignition coil 4.
5. This step tests for an open or a short in the ignition trigger signal circuit. The voltage on the ignition trigger signal circuit will fluctuate very quickly when starting or running the engine. The DMM voltage reading on the ignition trigger signal circuit should indicate 0.2-1 volt. Using the min/max feature on the DMM may indicate a maximum voltage as high as 3.5 volts.
11. This step tests for a fault in the Ignition Fail-Safe Input circuit. If the cause of the DTCs P0351, P0352, P0353, and P0354 is a fault in the ignition fail-safe input circuit, the engine will start and run for less than 2 seconds. Without the fail-safe signal the PCM will initiate fuel cutoff.
13. This step tests for a short in the ignition positive voltage supply to the ignition coils or for a faulty noise filter. A shorted noise filter may pull down the ignition coil primary voltage.