2010 Cadillac Truck SRX AWD V6-3.0L Page 1227
Circuit Description
The ECM supplies 5 V reference voltage, through the 5 V reference voltage circuit, to the S87 fuel economy mode switch. The 5 V reference
voltage causes current to flow through a series of resistors in the switch to the switch ground circuit. The ECM monitors the reference voltage
through a discrete fuel economy mode switch signal circuit. When the switch button is momentarily pressed, the switch contacts allow the 5 V
reference voltage to by-pass one of the resistors. The ECM detects the resulting voltage drop as a fuel economy mode request and sends a GMLAN
message to the transmission control module (TCM) indicating the request. When the TCM receives the request, throttle progressions and
transmission shift points are modified to optimize fuel efficiency. The instrument panel cluster (IPC) also receives the fuel economy mode request
message from the ECM and illuminates the fuel economy mode indicator lamp. The fuel economy mode switch must be pressed for between
0.094-1.5 s to activate the fuel economy mode.
Conditions for Running the DTC
* Ignition key must be turned to ON.
* DTCs P159F and P15A0 run continuously when the above condition is met.
Conditions for Setting the DTC
The ECM detects that the voltage on the fuel economy mode switch signal wire is either too low or too high out of range.
Action Taken When the DTC Sets
DTCs P159F and P15A0 are Type B DTCs
Conditions for Clearing the MIL/DTC
DTCs P159F and P15A0 are Type B DTCs
Reference Information
Schematic Reference
Engine Controls Schematics (LAU) (See: Diagrams/Electrical Diagrams/Powertrain Management/System Diagram)Engine Controls Schematics
(LF1) (See: Diagrams/Electrical Diagrams/Powertrain Management/System Diagram)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views/Connector End Views By Name)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (See: Diagnostic Trouble Code Descriptions/Powertrain Diagnostic Trouble Code
(DTC) Type Definitions)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning)for scan tool information
Circuit/System Verification
1. Ignition ON, verify the fuel economy mode indicator lamp on the instrument panel cluster is not illuminated.
2. Ignition ON, verify the fuel economy mode indicator lamp on the instrument panel cluster illuminates when the fuel economy mode switch
button is pressed.
3. Engine running, observe the scan tool DTC information. DTCs P159F and P15A0 should not set.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the
conditions that you observed from the Freeze Frame/Failure Records data.
