P1279

P1279-STARTER CONTROL CIRCUIT 2 OPEN

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

The Engine Stop/Start (ESS) system uses an In-Rush Current Relay (ICR) to reduce the voltage drop during an Auto Start event. The purpose of this is for the consumer electronics and vehicle subsystems to continue to function in a normal manner. The ICR is connected in-line of the main Battery feed to the Starter Motor.

The ICR is normally closed in the off position. This means that when it is de-energized, the relay is closed and full battery current is allowed to pass through the ICR directly to the Starter Motor with no resistance. During all key crank events the ICR is in this mode of operation and voltage drop is approximately 3.5 volts during cranking.

However, during an Auto Start crank event in ESS mode, the ICR is energized which opens the relay. When this occurs, battery current to the Starter Motor is diverted through the resistor inside the ICR and then to the Starter Motor. This reduces the voltage drop from approximately 2.0 volts during an Auto Start cranking event.

The ICR is energized when 12 volts is supplied to the coil by the ICR Control Relay, which is controlled the Powertrain Control Module (PCM).

- When Monitored:
With the ignition on and the ICR Control Relay commanded off.

- Set Conditions:
The Powertrain Control Module (PCM) detects an open condition in the ICR Control Relay control circuit. One trip fault.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. ACTIVE DTC
1. Test drive the vehicle in Stop/Start mode.
2. With the scan tool, view DTCs.

NOTE:
If the vehicle has a no crank condition and/or DTC P141D is present along with this DTC, try replacing Starter Relay 2 and recheck for fault being active before proceeding.

Is the DTC active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. CHECK THE (T762) ICR CONTROL RELAY CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the PDC C3 harness connector.
3. Disconnect the PCM C2 harness connector.
4. Measure the resistance of the (T762) ICR Control Relay Control circuit between the PDC C3 harness connector and the PCM C2 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 3

No

- Repair the (T762) ICR Control Relay Control circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. CHECK THE ICR CONTROL RELAY COIL SUPPLY
1. Remove Starter Relay 2 from the PDC.
2. Using a 12-volt test light connected to ground, probe the 12 volt supply circuit at the Starter Relay 2 connector (terminal 30).

NOTE:
Compare the brightness to that of a connection direct battery.

Is the test light illuminated and bright?

Yes

- Go To 4

No

- Repair the open 12 volt supply to the Starter Relay 2.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. CHECK THE ICR CONTROL RELAY
1. Connect a jumper across terminal 30 and terminal 87 of the Starter Relay 2 connector.
2. Measure the voltage of the (T762) ICR Control Relay Control circuit at the PDC C3 harness connector with the jumper in place.

Is the voltage equal to battery voltage?

Yes

- Go To 5

No

- Replace the PDC.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Power Distribution Center and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Switch and Powertrain Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module (PCM). Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.