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Engine Controls and Fuel - 3.0l or 3.6l - DTC p2534 - DTC p2636 Cadillac CTS II

Testing & Diagnostics ~2129 words

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen or High ResistanceShort to VoltageSignal Performance
IGN VoltageP2534P2534

Circuit/System Description

The fuel pump control module monitors the ignition voltage circuit in order to determine if the voltage is within the normal operating range.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The FPCM detects that the IGN voltage is less than 6.0 V.

Action Taken When the DTC Sets

DTC P2534 is a Type A DTC.

Conditions for Clearing the DTC

DTC P2534 is a Type A DTC.

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

  1. Verify that DTC P0562 is not set. If DTC P0562 is set, refer to «DTC P0562»(/cadillac/cts/ii-2007-2014/remont/charging-system/#battery-charging-system-and-starting-system) .
  2. Ignition OFF, disconnect the harness connector of the K27 fuel pump control module.
  3. Ignition ON, test for greater than 11 V between the IGN voltage circuit terminal 15 and ground. If less than the specified voltage, test the IGN voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ECM/TCM fuse is open, test the voltage circuit for a short to ground. If the circuit tests normal, test or replace the Run/Crank relay.
  4. If all circuits test normal, replace the K27 fuel pump control module.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Relay Replacement (Attached to Wire Harness)»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions) or «Relay Replacement (Within an Electrical Center)»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for fuel pump control module replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

To improve shift feel, the transmission control module (TCM) may request that the engine control module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding the injection timing and notifying the TCM that the request has succeeded. If the ECM is unable to comply with the request, the ECM sends the TCM a message that the request has failed.

The torque reduction request is sent to the ECM through GMLAN.

  1. The ignition is ON for greater than 3 seconds.
  2. The ignition voltage is between 10-18 volts.
  3. The DTCs run continuously once the above condition is met for greater than 10 mS.

The ECM detects an invalid signal from the TCM for greater than 1 second, or a cumulative of 10 seconds.

DTC P2544 is a Type C DTC.

DTC P2544 is a Type C DTC.

DTC Type Reference

Circuit/System Verification

  1. Observe the Freeze Frame/Failure Records with a scan tool.
  2. Clear the DTCs with a scan tool.
  3. Ignition OFF for 30 seconds.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If DTC P2544 failed this ignition, replace the TCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for TCM replacement, setup, and programming.

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
ControlP0231P023FP0232P023F, P2635
Low ReferenceP023FP023F, P2635

The engine control module (ECM) supplies voltage to the fuel pump control module when the ECM detects that the ignition is on. The voltage from the ECM to the fuel pump control module remains active for 2 seconds, unless the engine is in crank or run. While this voltage is being received, the fuel pump control module closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure.

  1. DTC P018B, P018C, P018D, P0231, P0232, P023F, P064A, P1255 or P06A6 are not active.
  2. DTC P0641 has not failed this ignition cycle.
  3. Fuel pump control is enabled and the fuel pump control state is normal.
  4. The system voltage is greater than 11 V.
  5. The engine has been running for more than 30 seconds.

This DTC sets when the fuel pump control module detects a predetermined fuel pressure performance degradation between the desired fuel rail pressure and the current estimated fuel rail pressure.

DTC P2635 is a Type B DTC.

DTC P2635 is a Type B DTC.

Diagnostic Aids

Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTCs P018C, P018D, P0231, P0232, or P023F are not set. If the DTC is set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  2. Ignition OFF, disconnect the harness connector at the G12 fuel pump.
  3. Ignition ON, test for less than 5.0 ohms between the G12 fuel pump low reference circuit terminal 2 and ground. If greater than the specified range, test the G12 fuel pump low reference circuit for a high resistance. If the circuit tests normal, replace the K27 fuel pump control module.
  4. Ignition OFF, install a test lamp between the control circuit terminal 1 and the low reference circuit terminal 2.
  5. Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K27 fuel pump control module. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K27 fuel pump control module.
  6. Perform the «Fuel System Diagnosis»(/cadillac/cts/ii-2007-2014/remont/testing-diagnostics/#engine-controls-and-fuel-30l-or-36l-symptom-troubleshooting-and-diagnosis) to verify proper fuel pressure. If the fuel pressure is not normal, replace the G12 fuel pump
  7. If all circuits test normal, replace the K27 fuel pump control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Fuel Tank Fuel Pump Module Replacement - Right Side»(/cadillac/cts/ii-2007-2014/remont/testing-diagnostics/#engine-controls-and-fuel-30l-or-36l-repair-instructions)
  2. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for fuel pump control module replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Circuit Description

The fuel tank on this vehicle is equipped with 2 fuel level sensors, one for each reservoir of the fuel tank. Fuel is transferred from the left side of the fuel tank to the right side of the fuel tank in order to ensure all of the usable fuel volume is available. The fuel pump supplies a small amount of pressurized fuel to the siphon jet pump through the fuel feed pipe. The pressurized fuel creates a venturi action inside the siphon jet pump. The venturi action causes the fuel to be drawn out of the left side of the fuel tank. Fuel is then transferred from the left side of fuel tank to the right side of fuel tank through the internal fuel transfer tube. This diagnostic tests for too large of a difference in fuel level between the left and right side of the fuel tank. The DTC sets if the control module determines that the right side fuel level is less than a predetermined amount of the left side fuel level.

The following table illustrates the difference between fuel level, resistance, and voltage

Fuel Level-Right or Left SensorFuel Level Sensor ResistanceFuel Level Sensor Voltage
EmptyLowLow
FullHighHigh
  1. Before the engine control module (ECM) can report DTC P2636 failed, DTCs P0461, P0462, P0463, P2066, P2067, and P2068 must run and pass.
  2. The ignition 1 signal parameter is between 10-18 volts.
  3. The engine speed is greater than 240 RPM.
  4. DTC P2636 runs continuously once the above conditions exist for greater than 4 minutes.

The ECM detects that the right side fuel level is less than 11 percent and the left side fuel level is greater than 22 percent.

DTC P2636 is a Type C DTC.

Conditions for Clearing the MIL/DTC

DTC P2636 is a Type C DTC.

Depending on the current fuel level, it may be difficult to locate a malfunctioning fuel level sensor. The condition may only occur when the fuel level is full or near empty. The fuel level sensor unit may need to be removed for further diagnosis. A fuel level sensor that has an intermittent condition causes this DTC to set.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Scan Tool Reference

Control Module References for scan tool information

  1. Engine idling for 5 minutes, observe the DTC information with a scan tool. DTC P2636 should not set.
  2. 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.
  1. Ignition OFF, disconnect the harness connector of the left side fuel level sensor.
  2. Ignition ON, verify the scan tool Fuel Level Sensor Left Tank voltage parameter is at 5.0 V. If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  3. Install a 3 A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool Fuel Level Sensor Left Tank voltage parameter is at 0.0 V. If greater than the specified value, test the signal circuit for a high resistance. If the circuit tests normal, replace the ECM.
  4. Install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal D. Verify the scan tool Fuel Level Sensor Left Tank voltage parameter is at 0.0 V. If greater than the specified value, test the low reference circuit for a high resistance. If the circuit tests normal, replace the ECM.
  5. Remove the fuel tank.
  6. Remove the fuel tank primary and secondary fuel pump modules and inspect for the following conditions: A clogged secondary fuel strainer and pick up A clogged or restricted siphon jet pump Broken, clogged or restricted flex tubes, primary fuel tank module Broken, clogged, disconnected, or restricted fuel transfer tube inside tank If you find any of the above conditions, repair as necessary.
  7. If all circuits/connections test normal, test or replace the left/secondary fuel level sensor.

Component Testing

  1. Ignition OFF, remove the left fuel level sensor from the fuel tank.
  2. Connect a DMM between terminal A and terminal D.
  3. Verify the secondary fuel level sensor resistance remains within 40-250 ohms and changes smoothly while moving the float arm from stop to stop. If not within the specified range or changes erratically while moving the float arm from stop to stop, replace the fuel level sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Fuel Tank Fuel Pump Module Replacement - Right Side»(/cadillac/cts/ii-2007-2014/remont/testing-diagnostics/#engine-controls-and-fuel-30l-or-36l-repair-instructions)
  2. «Fuel Level Sensor Replacement - Left Side»(/cadillac/cts/ii-2007-2014/remont/testing-diagnostics/#engine-controls-and-fuel-30l-or-36l-repair-instructions)
  3. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for engine control module replacement, setup, and programming

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