P0351

Circuit Description
The powertrain Control module (PCM)/engine Control module (ECM) provides a ground for the electronic spark timing B circuit. When the PCM/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 PCM/ECM and the electronic ignition system is monitored for an open circuit, short to voltage, and short to ground. When the PCM/ECM detects a problem in the spark timing B circuit, it will set DTC P0351.

Conditions for Setting the DTC
- Ignition ON.
- Time of fault fall occurrence is greater than the time of the EST fall occurrence.
- The EST fault occurs on falling edge.
- Must receive more than 40 failures within 80 test cycles.

Action Taken When the DTC Sets
- The PCM/ECM will illuminate the Malfunction Indicator Lamp (MIL) the first time the fault is detected.
- The PCM/ECM will store conditions which were present when the Diagnostic Trouble Code (DTC) was set as Freeze Frame and in the Failure Records data.
- Low speed Cooling fan turns On.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The PCM/ECM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P0351 will clear after 40 consecutive warm up cycles have occurred without a fault.
- DTC P0351 can be cleared by using the scan tool.

Steps 1 - 9:

Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the insulation. Check for:
- Poor connection - Inspect the PCM/ECM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
- Damaged harness - Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM/ECM, turn the ignition on, and observe a voltmeter connected to the 58X reference circuit at the PCM/ECM harness connector while moving connectors and wiring harnesses related to the PCM/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.