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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0027

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0027: Exhaust Throttle Control Valve Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open

Short to Voltage

Exhaust Brake and Exhaust Throttle Solenoid Control Circuit

P0079

P0079

P0080

Circuit/System Description

The exhaust throttle solenoid is installed to the frame near the exhaust throttle valve of the exhaust pipe. When the diesel particulate filter (DPF) regeneration mode is ON and the exhaust brake is ON , then the exhaust throttle solenoid is turned ON by the engine control module (ECM). The ECM detects an open or closed position of a valve from the mass air flow (MAF) value and an engine speed.

Conditions for Running the DTC
    • DTCs P0079, P0080, P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0126, P0201, P0202, P0203, P0204, P0205, P0206, P02E7, P02E8, P0335, P0336, P0403, P0404, P0409, P0506, P0507, P0602, P0652, P0653, P1125, P1293, P2002, P2100, P2146, P2147, P2148, P2149, P2150, P2151, P2161, P2164, P2167, P2170, P2173, P2176, P2227, P2228, P2229, P2454, and P268A are not set.
    • The battery voltage is between 10-16 volts.
    • The engine is running for longer than 5 seconds.
    • The engine speed is between 450-1,000 RPM.
    • The engine coolant temperature (ECT) is between 60-90°C (140-194°F).
    • The intake air temperature (IAT) is between -10 and +119°C (+14 and +246°F).
    • The barometric pressure (BARO) is more than 75 kPa.
    • The accelerator pedal position is less than 3 percent.
    • The vehicle speed is less than 3 km/h (2 mph).
    • The DPF differential pressure is between -10 and +20 kPa.
    • The exhaust brake command is OFF.
    • The exhaust throttle command is ON.
    • The power take-off (PTO) control is not active.

Conditions for Setting the DTC
    • The ECM detects that the exhaust throttle systems closed stuck condition or open stuck condition.
    • The main input is the engine speed and the MAF value.

Action Taken When the DTC Sets

DTC P0027 is a Type A DTC.

Conditions for Clearing the MIL/DTC

DTC P0027 is a Type A DTC.

Diagnostic Aids

Inspect for any recent engine mechanical repairs. An incorrectly installed exhaust throttle solenoid exhaust throttle will cause this DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
    • If DTC P0079, P0080, P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0126, P0201, P0202, P0203, P0204, P0205, P0206, P02E7, P02E8, P0335, P0336, P0403, P0404, P0409, P0506, P0507, P0602, P0652, P0653, P1125, P1293, P2002, P2100, P2146, P2147, P2148, P2149, P2150, P2151, P2161, P2164, P2167, P2170, P2173, P2176, P2227, P2228, P2229, P2454 and P268A are set, test and repair those DTCs first.
    • Verify the integrity of the air induction system by inspecting for the following conditions:
       - Damaged components
       - Restrictions in the MAF air induction system

Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Ignition OFF, disconnect the harness connector at the mass air flow (MAF) sensor.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 4 and ground.
    3. ⇒If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 3 and ground.
    4. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  4. Verify the scan tool MAF parameter is less than 1 g/s.
    5. ⇒If greater than 1 g/s, test the signal circuit terminal 5 for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Install a 3A fused jumper wire between the signal circuit terminal 5 and the ignition circuit terminal 3. Verify the scan tool MAF parameter is more than 500 g/s.
    6. ⇒If less than 500 g/s, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. If all circuits test normal, replace the MAF sensor.
  7. Ignition OFF, disconnect the harness connector at the exhaust throttle solenoid.
  8. Ignition ON, verify that a test lamp illuminates between the power supply circuit and ground.
    9. ⇒If the test lamp does not illuminate, test the power supply circuit for a short to ground or an open/high resistance.
  9. Ignition OFF, disconnect the harness connector at the ECM.
  10. Install a 3A fused jumper wire between the power supply circuit and the control circuit at the exhaust throttle solenoid.
  11. Ignition ON, verify that a test lamp illuminates between the control circuit at ECM and ground.
    12. ⇒If the test lamp does not illuminate, test the power supply circuit for a short to ground or an open/high resistance.
  12. Ignition OFF, test for 15-20 ohms at the solenoid terminal.
    13. ⇒If not within 15-20 ohms, replace the solenoid. If the solenoid tests normal, replace the ECM.
  13. Inspect the exhaust throttle.
    14. ⇒If abnormal condition detected, replace the exhaust throttle.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Exhaust Throttle Replacement
    •  Mass Airflow Sensor/Intake Air Temperature Sensor Replacement
    •  Control Module References for ECM replacement, setup, and programming