Circuit Description
The powertrain control module (PCM) receives an engine start signal from the ignition switch when the engine cranking. The engine start signal will pass through either the clutch pedal position switch or the transaxle range switch. The PCM increases the fuel that is injected for improved starting when the engine start signal is present. The engine will start without the PCM receiving the engine start signal.
Conditions for Setting the DTC
| • | There is not an engine start signal to the PCM when engaging the starter. |
| • | There is low voltage at the PCM while the engine is cranking. |
| • | There is a high voltage at the PCM after starting the engine. |
| • | The condition occurs once per drive cycle for 0.4 seconds. |
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM will record operating conditions at the time that the diagnostic fails. The Freeze Frame buffer stores this information. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutive trips, during which the diagnostic runs and a fault is not detected. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the Clear DTC Information function on the scan tool, or disconnect the PCM battery feed in order to clear the DTC. |
Diagnostic Aids
A fault in the CPP switch electrical circuit or in the transaxle range switch circuit may cause an intermittent malfunction. Inspect the wiring harness and the components for any of the following conditions:
| • | Backed out terminals |
| • | Incorrect mating of terminals |
| • | Broken electrical connector locks |
| • | Incorrectly formed terminals or damaged terminals |
| • | Faulty terminal-to-wire connections |
| • | Physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Corrosion of electrical connections, of splices, or of terminals |
If a DTC P1500 cannot be duplicated, the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.
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This step determines that the fault is present.
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While the engine is cranking, the PCM should receive 6 to 12 volts on the engine start circuit. An engine that is running should have 0.0 volts on the engine start circuit.
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Unless a short to voltage is indicated, the PCM shows zero voltage on the engine start circuit if the engine is running.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is a DTC P1500 set? | -- | Go to Diagnostic Aids | ||
Is the voltage near the specified range while cranking the engine? | 6-12 V | |||
4 | For a manual transaxle, repair the open or the short in the engine start circuit between the PCM and the clutch pedal position switch. For an automatic transmission, repair the open or the short in the engine start circuit between the PCM and the transaxle range switch. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
Measure the voltage at the PCM electrical connector of the engine start circuit with the engine running. Is the voltage at the specified value? | 0 V | |||
6 | Repair the short to voltage in the engine start circuit between the PCM and either the transaxle range switch or the clutch pedal position (CPP) switch. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
7 |
Was repair necessary? | -- | ||
8 | Replace the PCM. Is the action complete? | -- | -- | |
9 |
Does the scan tool display any DTCs? | -- | Go to the applicable DTC table | System OK |
