• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Underhood Fuse Block B+ | 1 | 1 | -- | -- |
IGN A Fuse | -- | 1 | -- | -- |
IGN E Fuse | -- | 1 | -- | -- |
Park Neutral Signal | 1 | 1 | 2 | -- |
Starter Relay Coil Control | 3 | 1 | 1 | -- |
Starter Solenoid Crank Voltage | 1 | 1 | 3 | -- |
1. No crank 2. Cranks in any gear 3. Cranks all the time |
The engine control module (ECM) controls engine cranking based on a power mode input and the status of the park/neutral position (PNP) switch. With the transmission in Park/Neutral, voltage at the ECM PNP switch signal circuit is high. This indicates to the ECM that conditions are acceptable for cranking. When a crank request power mode is seen, the ECM applies ground to the starter relay coil control circuit. This energizes the coil side of the relay, which pulls the switch side of the relay closed, applying voltage to the starter terminal A (4.2L) or S (5.3L) and engaging the starter solenoid.
• | Inspect the IGN A fuse and the IGN E fuse for an open. |
• | A misadjusted PNP switch or range selector lever cable may result in a starter solenoid does not click condition. |
Starting System Description and Operation
Control Module References for scan tool information
⇒ | If not the specified value, refer to PNP Switch Circuit Malfunction. |
⇒ | If the solenoid does not engage, refer to STRTR Relay Circuit Malfunction. |
⇒ | If the solenoid engages but the engine does not crank, refer to Starter Solenoid Clicks, Engine Does Not Crank . |
⇒ | If the test lamp does not illuminate, test the ignition circuit for an open/high resistance. |
⇒ | If not the specified value, test the signal circuit terminal 1 for a short to voltage. If the circuit tests normal, replace the ECM. |
⇒ | If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the signal circuit for an open/high resistance. |
⇒ | If the test lamp is always ON, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the ECM. |
⇒ | If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
Important: The engine may begin to crank.
⇒ | If the test lamp does not illuminate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, test or replace the STRTR relay. |
• | R |
• | OD |
• | D |
• | 2 |
• | 1 |
⇒ | If not the specified value, replace the PNP switch. |
• | P |
• | N |
⇒ | If greater than the specified range, replace the PNP switch. |
⇒ | If not within the specified range, replace the relay. |
• | 30 and 86 |
• | 30 and 87 |
• | 30 and 85 |
• | 85 and 87 |
⇒ | If not the specified value, replace the relay. |
⇒ | If greater than specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for BCM or ECM replacement, setup and programming. |