Schematic Reference: Engine Controls Schematics
Circuit Description
While the engine is being cranked, the battery voltage is applied to the powertrain control module (ECM). The starter signal is mainly used to increase the fuel injection volume for the starting injection control. This signal is sent from the transmission range switch (automatic transmission) or the clutch pedal position (CPP) switch. If this signal is not detected during ignition, the ECM will still allow the engine to start.
Conditions for Setting the DTC
| • | No signal to the ECM with the starter engaged. |
| • | Low voltage at the ECM while cranking the engine. |
| • | High voltage at the ECM after starting the engine. |
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 ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn off after three consecutive drive cycles without a fault present. |
| • | A DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | The DTCs can be cleared by using a scan tool or by disconnecting the ECM battery feed. |
Diagnostic Aids
An intermittent malfunction may be caused by a fault in the starter signal sensor circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connector locks. |
| • | Improperly formed or damaged terminals. |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, splices, or terminals. |
| • | An incorrectly adjusted TP sensor could cause a DTC P0510 to set. Refer to Throttle Position Sensor Adjustment |
If a DTC P1500 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first 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 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.
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This step determines if a fault is present.
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This step checks for the correct voltage on the crank signal circuit. While the engine is cranking, the ECM crank signal terminal should have a voltage reading of 6 to 12 volts and after the engine is started, the ECM crank signal terminal should have a voltage reading of 0 volts.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is DTC P1500 set? | -- | Go to Diagnostic Aids | ||
Is the voltage near the specified value? | 6 to 12 volts | |||
4 | Repair the open or the short in the crank signal circuit between the ECM and the transmission range switch (A/T) or the clutch pedal position (CPP) switch (M/T). Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
5 |
Was a repair necessary? | -- | ||
6 | Replace the ECM. Refer to Engine Control Module Replacement. Is the action complete? | -- | -- | |
7 |
Are any DTCs displayed on the scan tool? | -- | Go to the Applicable DTC Table | System OK |
