GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 7.8L (LF8) 🢒 DTC P0237 or P0238

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 Descriptors

DTC P0237: Turbocharger Boost Sensor Circuit Low Voltage

DTC P0238: Turbocharger Boost Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open

Short to Voltage

5-Volt Reference Circuit

P0192, P02E8, P0409, P0462, P0642, P2453, P2454, P2564

P0237

--

Signal Circuit

P0237

P0237

P0238

Ground Circuit

--

P0238

--

Typical Scan Tool Data

Boost Pressure Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Boost Pressure Sensor

Parameter Normal Range: 00-255 kPa

Boost Pressure Sensor 5-Volt Reference Circuit

33 kPa

33 kPa

--

Boost Pressure Sensor Signal Circuit

33 kPa

33 kPa

255 kPa

Boost Pressure Sensor Ground Circuit

33 kPa

255 kPa

--

Circuit/System Description

The engine control module (ECM) supplies 5 volts to the boost pressure sensor on the 5-volt reference circuit. The ECM also provides a ground on the low reference circuit. The boost pressure sensor provides a signal to the ECM on the boost pressure signal circuit which is relative to the pressure changes in the manifold. The ECM should detect a low signal voltage at a low boost pressure, such as low engine load. The ECM should detect high signal voltage at a high boost pressure, such as high engine load. The ECM monitors the boost pressure sensor signal for voltage outside the normal range of the boost pressure sensor.

Conditions for Running the DTC

P0237

    • DTCs P0238, P02E7, P02E8, P0642, P0643, P2228 and P2229 are not set.
    • The battery voltage is between 10-16 volts.
    • The ignition is ON for longer than 2 seconds.

P0238

    • DTCs P0237, P0642, and P0643 are not set.
    • The battery voltage is between 10-16 volts.
    • The ignition is ON for longer than 2 seconds.

Conditions for Setting the DTC

P0237

The ECM detects that the boost pressure sensor signal voltage is less than 0.1 volt.

P0238

The ECM detects that the boost pressure sensor signal voltage is more than 4.8 volts.

Action Taken When the DTC Sets

DTCs P0237 and P0238 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P0237 and P0238 are Type A DTCs.

Diagnostic Aids

An incorrectly installed turbo charger boost sensor 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

Important: If DTC P02E7, P02E8, P0642, P0643, P2228 and P2229 are set, test and repair those DTCs first.

    • Damaged components
    • Loose or improper installation

Circuit/System Testing

Important: Perform the Circuit/System Verification before proceeding with Circuit/System Testing.

P0237

  1. Turn ON ignition, with the engine OFF.
  2. Disconnect the turbocharger boost sensor connector, connect a DMM between the turbocharger sensor 5-volt reference circuit and ground, and measure the voltage
    3. ⇒If the voltage is not 0-4.75 volts, test for an open or short to ground in the 5-volt reference circuit. If the circuits test normal, replace the control module.
  3. Observe the turbocharger boost parameter with a scan tool.
    4. ⇒If boost pressure is less than 33 kPa (4.7 psi), test the turbocharger boost sensor signal circuit for a short to ground or an open. If the circuits test normal, replace the turbocharger boost sensor.
  4. Connect a fused jumper between the turbocharger boost sensor signal circuit and the low reference circuit and observe the boost pressure parameter with a scan tool.
    5. ⇒If boost pressure goes to 255 kPa (37 psi), replace the turbocharger boost sensor.
    ⇒If boost pressure does not change, replace the control module.

P0238

  1. Turn ON ignition, with the engine OFF.
  2. Disconnect the turbocharger boost sensor connector, connect a DMM between the turbocharger sensor 5-volt reference circuit and ground, and measure the voltage
    3. ⇒If the voltage is not 0-4.75 volts, test for an open or short to ground in the 5-volt reference circuit. If the circuits test normal, replace the control module.
  3. Observe the turbocharger boost parameter with a scan tool.
    4. ⇒If boost pressure is more than 250 kPa (36.3 psi), test the turbocharger boost sensor signal circuit for a short to ground or an open. If the circuits test normal, replace the turbocharger boost sensor.
  4. Connect a fused jumper between the turbocharger boost sensor signal circuit and the low reference circuit and observe the boost pressure parameter with a scan tool.
    5. ⇒If boost pressure is less than 33 kPa (4.7 psi), replace the turbocharger boost sensor.
    ⇒If boost pressure does not change, test the signal circuit and the low reference circuit for an open. If the circuits test normal, replace the control module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Manifold Absolute Pressure Sensor Replacement
    •  Control Module References for ECM replacement, setup, and programming