2008 Cadillac SRX 3.6 L Code P2138 some times code 2122
DTC P2138: Accelerator Pedal Position (APP) Sensor 1-2 Correlation
P2138
• The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 0.23 volt, 0.25 volt for LLT, with the pedal released.
• The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 0.29 volt, 0.31 volt for LLT, with a partially pressed pedal.
• The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 1.66 volts, 1.70 volts for LLT, with a fully pressed pedal.
• Any of the above conditions exist, then a 5 second delay for MIL ON.
Diagnostic Aids
Test the current output of the 5-volt reference circuits if you suspect high resistance in the circuit. The current output should be greater than 80 mA for APP 1 and greater than 50 mA for APP 2.
If you don't know how to test the 5 volt reference circuits you need to take it to a qualified repair shop.
Circuit/System Verification
Ignition ON, observe the DTC information with a scan tool. DTC P0651, P0652, P0653, P0697, P0698, or P0699 should not be set.
? If a DTC is set, refer to DTC P0641-P0643, P0651-P0653, or P0697-P0699.
Observe the scan tool APP Sensor voltage parameters. Verify both of the APP sensor voltages are between 0.74-4.82 V.
Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTCs P2122, P2123, P2127, P2128, or P2138 should not set.
Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTCs P2122, P2123, P2127, P2128, or P2138 should not set.
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.
Circuit/System Testing
Ignition OFF, remove the fuse that supplies B+ to terminal 56-X2 of the ECM.
Disconnect the harness connector at the accelerator pedal assembly.
Test for less than 5 ? between the appropriate low reference circuit of the APP sensor and ground.
? If greater than the specified range, test the low reference circuit of the APP sensor for a short to voltage, or an open/high resistance. If the circuit/connections test normal, replace the ECM.
Install the fuse that supplies B+ to terminal 56-X2 of the ECM.
Note: The 5-volt reference circuit voltage can be within the specified range with a high resistance in the circuit. If this condition is suspected, refer to Diagnostic Aids.
Ignition ON, test for 4.8-5.2 V between the appropriate 5-volt reference circuit of the APP sensor and ground.
? If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit/connections test normal, replace the ECM.
? If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
Observe the appropriate scan tool APP sensor voltage parameter. Verify the voltage is less than 0.3 volt.
? If greater than the specified range, test the signal circuit of the applicable APP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.
Connect a 3 A fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit of the APP sensor. Verify the APP sensor voltage parameter is greater than 4.8 V.
? If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.
? If both APP sensor voltage parameters display greater than 4.8 V test the signal circuits of the APP sensors for a shorted together condition. If the circuit/connections test normal, replace the ECM.
If all circuits/connections test normal, test or replace the accelerator pedal assembly.