DTC P0236. GMC Truck TopKick C-Series (Conventional) C4/C5 2004

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls - 6.6L (LB7) 🢒 DTC P0236

Circuit Description

The boost pressure sensor responds to pressure changes in the intake manifold. This pressure is created by the turbocharger and changes with accelerator pedal position (APP) and engine speed. The engine control module (ECM) uses this information to assist in the diagnosis of the barometric pressure (BARO) sensor and to provide engine overboost protection. The boost sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. ECM supplies 5 volts to the boost sensor on the 5-volt reference 2 circuit, and provides a ground on a low reference circuit. The boost sensor provides a signal to the ECM on a signal circuit relative to the pressure changes. The ECM monitors the boost pressure sensor signal for voltage outside of the normal range. The ECM calculates a predicted value for the boost sensor. The ECM then compares the predicted value to the actual signal. This DTC will set if the boost sensor signal is below the predicted range.

Conditions for Running the DTC

•	DTC P0237 is not set.

•	The engine speed is between 500-2,700 RPM.

•	The total fuel quantity burned is more than 2,000 mm³.

•	The coolant temperature is more than 72°C (158°F).

Conditions for Setting the DTC

The actual boost pressure sensor signal is below the predicted range by 50 kPa for 12 seconds.

Action Taken When the DTC Sets

•	The control module stores the DTC information into memory when the diagnostic runs and fails.

•	The malfunction indicator lamp (MIL) will not illuminate.

•	The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

•	The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

•	A current DTC Last Test Failed clears when the diagnostic runs and passes.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

•	Clear the DTC with a scan tool.

Test Description

The number below refer to the step number on the diagnostic table.

With the ignition ON and the engine OFF, the BARO sensor and the boost sensor should indicate the current barometric pressure. A significant difference between the readings indicates an electrical fault.

The spring in the wastegate actuator should return the wastegate via the linkage back to the closed position.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Start the engine.
Allow the engine to reach operating temperature.
Turn OFF the ignition.
Turn ON the ignition, with the engine OFF.
Observe the BARO sensor and the boost sensor with a scan tool.
Compare the BARO sensor pressure to the Boost sensor pressure .

Is the boost sensor pressure less than the BARO sensor pressure by more than the specified value?

10 kPa

Go to Step 9

Go to Step 3

Turn OFF the ignition.
Remove the boost sensor from the intake manifold. Refer to Boost Sensor Replacement .
Inspect for the following conditions:

•	A plugged sensor port

•	A damaged seal

Did you find and correct the condition?

Go to Step 18

Go to Step 4

Reconnect the boost sensor electrical connector.
Turn ON the ignition, with the engine OFF.
Connect a hand vacuum pump to the sensor port.
Observe the boost sensor pressure on the scan tool as you SLOWLY apply vacuum 1 inch Hg at a time up to 15 inches Hg. Each inch of vacuum should result in a 3-4 kPa drop in pressure.

Does the scan tool indicate the boost sensor is operating normally?

Go to Step 5

Go to Step 9

Disconnect the hand vacuum pump from the sensor.

Does the scan tool indicate that the boost sensor pressure returns to the value observed in step 2?

Go to Step 6

Go to Step 16

Inspect for the following conditions:

•	A restriction in the exhaust system. Refer to Restricted Exhaust in Engine Exhaust.

•	A restriction in the air cleaner or the intake tube

•	A leaking charge air cooler with a J 46091 charge air cooler tester

•	A leaking charge air pipes and connecting clamps and hoses

•	A leaking intake manifold

•	An exhaust brake that is stuck ON. Refer to Exhaust Brake Always On in Engine Exhaust.

Did you find and correct the condition?

Go to Step 18

Go to Step 7

Caution: Wear safety glasses when using compressed air in order to prevent eye injury.

Turn OFF the ignition.
Remove the hose from the wastegate actuator tube.
Apply compressed air, not exceeding 45 psi, to the actuator tube to open the wastegate. The wastegate should begin to open near 30 psi and be fully open at 45 psi. The actuator rod stroke should measure near 4 mm.
Remove the compressed air from the actuator tube.

Does the wastegate move to the fully extended position and return to the fully retracted position?

Go to Step 8

Go to Step 15

Remove the Air intake Pipe from the turbocharger.
Inspect for any condition that may cause poor turbocharger performance. Refer to Turbocharger Cleaning and Inspection in Engine Mechanical.

Did you find a problem with the turbocharger?

Go to Step 15

Go to Intermittent Conditions

Disconnect the boost sensor electrical connector. Refer to Boost Sensor Replacement .
Connect a test lamp to a good ground.
Probe the 5-volt reference circuit of the boost sensor with the test lamp.

Does the test lamp illuminate?

Go to Step 10

Go to Step 11

Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the boost sensor and the signal circuit of the boost sensor.

Does the scan tool indicate that the pressure is more than the specified value?

254 kPa

Go to Step 13

Go to Step 12

Test the 5-volt reference circuit of the boost sensor for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the conditions?

Go to Step 18

Go to Step 14

Test the signal circuit of the boost sensor for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 14

Inspect for poor connections at the boost pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 16

Inspect for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 17

Replace the turbocharger. Refer to Turbocharger Replacement in Engine Mechanical.

Did you complete the replacement?

Go to Step 18

Replace the boost sensor. Refer to Boost Sensor Replacement .

Did you complete the replacement?

Go to Step 18

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

Go to Step 18

Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 19

Go to Step 2

Observe the stored information in Capture Info. with a scan tool.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK