Circuit Description
The engine control module (ECM) provides a ground for the electronic spark timing A circuit. When the ECM removes the ground path of the ignition primary coil, the magnetic field produced by the coil collapses. The collapsing magnetic field produces a voltage in the secondary coil which fires the spark plug.
The circuit between the ECM and the electronic ignition system ignition coil is monitored for an open circuit, short to voltage, and short to ground. When the ECM detects a problem in the electronic spark timing A circuit, it will set DTC P0351.
Conditions for Setting the DTC
| • | Monitor the fault feedback signal. |
| • | The ignition is ON. |
| • | A fault flag increments fail count. |
| • | Must receive more than 200 failures within 255 test cycles. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | The low speed coolant fan turns ON. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside the insulation. Inspect for:
| • | A poor connection--Inspect the ECM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal-to-wire connection. |
| • | A damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the ECM, turn the ignition ON, and observe a voltmeter connected to the 58X reference circuit at the ECM harness connector while moving connectors and wiring harnesses related to the ECM. A change in voltage will indicate the location of the fault. |
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Step | Action | Yes | No |
|---|---|---|---|
1 | Perform an On-Board Diagnostic System Check. Was the check performed? | Go to Step 2 | |
2 | Inspect for a faulty connection or damaged terminal C at the electronic ignition (EI) system ignition coil and repair as needed. Did you find and correct the condition? | Go to Step 8 | Go to Step 3 |
3 | Inspect for a faulty connection or damaged terminal A19 at the engine control module (ECM) and repair as needed. Did you find and correct the condition? | Go to Step 8 | Go to Step 4 |
4 |
Did you find and correct the condition? | Go to Step 8 | Go to Step 5 |
5 | Inspect the ignition control circuit for a short to voltage and repair as necessary. Did you find and correct the condition? | Go to Step 8 | Go to Step 6 |
6 | Inspect for an open ignition control circuit and repair as needed. Did you find and correct the condition? | Go to Step 8 | Go to Step 7 |
7 |
Did you complete the replacement? | Go to Step 8 | -- |
8 |
Does the scan tool indicate that this diagnostic ran and passed? | Go to Step 9 | Go to Step 2 |
9 | Are any DTCs displayed that have not been diagnosed? | Go to applicable DTC table | System OK |
