Circuit Description
The crankshaft position sensor provides a signal to the powertrain control module (PCM) which generates the 12x and 2x signals. The starter generator control module (SGCM) shall calculate the speed and position of the engine by using the 12x and 2x signals generated by the PCM. The SGCM shall use the engine speed message sent by the PCM over the GMLAN bus to verify the speed calculated using the 12x and 2x signals. The 12x and 2x signals shall be used to calculate the engine position.
The 12x signal is a pulsed signal calculated by the PCM to represent engine speed. This is a square wave where 12 pulses represent one 360 degrees revolution of the engine. This signal is used by the SGCM to determine engine speed.
The 2x signal is a pulsed signal calculated by the PCM to represent engine speed. This is a square wave where 2 pulses represent one 360 degrees revolution of the engine. This signal is used to determine engine speed.
Both signals are used to determined engine position.
When these signals are out of synchronization, a DTC will set.
The SGCM has 2 discrete crank signal circuit inputs to calculate engine position. One is hard wired and one is a signal on the GMLAN bus. This acts as a back-up system. In the event that one signal is interrupted, the engine will be able to start and run, although a DTC will set.
The following DTCs are for faults with the engine speed signal circuits and internal failures within the SGCM.
| • | P0616 Starter Relay Control Circuit Low Voltage |
| • | P0617 Starter Relay Control Circuit High Voltage |
| • | P2617 Crankshaft Position Signal Output Circuit |
| • | P0725 Engine Speed Circuit |
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC P0616 Starter Relay Control Circuit Low Voltage |
| • | DTC P0617 Starter Relay Control Circuit High Voltage |
| • | DTC P2617 Crankshaft Position Signal Output Circuit |
| • | DTC P0725 Engine Speed Circuit |
Conditions for Running the DTC
| • | Engine running for 30 seconds. |
| • | The SGCM has received voltage on the ignition 0 voltage circuit. |
| • | The SGCM has turned ON and no configuration DTC are present. |
| • | This diagnostic shall be run every 100 ms. |
| • | Reference voltage is stable and accurate. |
Conditions for Setting the DTC
P0616
Crank request signal is true and PCM key crank enable signal is no crank.
P0617
Crank request signal is false and PCM key crank enable signal is crank.
P2617
The 12x and 2x signals differ from each other by more than 3.5 percent.
P0725
The 12x and 2x signals differ from each other by more than 6 percent.
Action Taken When the DTC Sets
| • | The PCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The driver information center (DIC), if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Starting and Charging Schematics Connector End View Reference: Engine Electrical Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Is the DTC set as current DTC? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections |
3 | Inspect for poor connections at the harness connector of the SGCM . Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 5 | Go to Step 4 |
4 | Replace the SGCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 5 | -- |
5 |
Does the DTC reset? | Go to Step 2 | System OK |
