The boost pressure sensor measures the pressure inside the intake manifold. Pressure in the intake manifold is affected by turbocharger output, engine speed, accelerator pedal input, air temperature, and barometric pressure (BARO). A diaphragm within the boost pressure sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine. The sensor translates this action into electrical resistance. The boost pressure sensor wiring includes 3 circuits. The engine control module (ECM) supplies a regulated 5 volts to the sensor on a 5-volt reference circuit. The ECM supplies a ground on a low reference circuit. The boost pressure sensor provides a signal voltage to the ECM, relative to pressure, on the boost pressure sensor signal circuit. The ECM converts the signal voltage input to a pressure value. Under normal operation the lowest pressure that can exist in the intake manifold is equal to the BARO. This occurs when the vehicle is operated at idle or when the ignition is on while the engine is off. Under these conditions, the ECM uses the boost pressure sensor to aid in diagnosis of the BARO sensor. The highest manifold pressures occur when the turbocharger output is high. Manifold pressure can range from 58 kPa (8 psi) when pressures are low to more than 240 kPa (34 psi) when pressures are high, depending on the BARO. The boost pressure sensor has a range of 33 kPa (4 psi) to 255 kPa (36 psi). The ECM also uses the boost pressure sensor to provide engine overboost protection. The ECM calculates a predicted value for the boost pressure sensor. The ECM then compares the predicted value to the sensor input. If the ECM detects that the boost pressure sensor input is below the predicted range, this DTC will set.
This diagnostic procedure supports the following DTC:
DTC P0299 Turbocharger Engine Underboost
• | DTCs P0237, P2227, P2228, or P2229 are not set. |
• | The engine speed is between 500-3600 RPM. |
• | The engine speed does not vary more than 50 RPM. |
• | The engine run time is more than 10 seconds. |
• | The ECM detects that the boost pressure input is 35 kPa below the calibrated value. |
OR |
• | To obtain the desired boost, the ECM must command the turbocharger vanes closed further than expected. |
• | One of the above conditions exist for more than 12 seconds. |
• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | 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 emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
Step | Action | Values | Yes | No | ||||||||||||||||
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Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||||||||||||||
2 |
Is DTC P0045, P0046, P0652, P2563, P2564, or P2565 also set? | -- | Go to Step 3 | |||||||||||||||||
3 | Observe the Boost Pressure Sensor parameter and the BARO parameter with a scan tool. Is the difference between the values more than the specified value? | 3 kPa | Go to Step 12 | Go to Step 4 | ||||||||||||||||
4 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 5 | ||||||||||||||||
5 |
Does the Boost Pressure Sensor parameter decrease? | -- | Go to Step 6 | Go to Step 20 | ||||||||||||||||
6 |
Does the Boost Pressure Sensor parameter return to the value observed in Step 3? | -- | Go to Step 7 | Go to Step 20 | ||||||||||||||||
7 | Inspect the following components:
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 8 | ||||||||||||||||
8 | Test the charge air cooler and connecting pipes and hoses for air leaks using the J 46091 Charge Air Cooler Tester. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 9 | ||||||||||||||||
9 | Inspect the exhaust system for the following conditions:
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 10 | ||||||||||||||||
10 | Remove and inspect the turbocharger for wear or damage. Refer to Turbocharger Replacement and Turbocharger Cleaning and Inspection in Engine Mechanical. Did you find a condition with the turbocharger? | -- | Go to Step 22 | Go to Step 11 | ||||||||||||||||
11 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Intermittent Conditions | ||||||||||||||||
12 | Test for an intermittent and for a poor connection at the boost pressure sensor connector. 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 23 | Go to Step 13 | ||||||||||||||||
13 |
Is the amperage more than the specified value? | 170 mA | Go to Step 14 | Go to Step 15 | ||||||||||||||||
14 |
Is the pressure more than the specified value? | 254 kPa (36 psi) | Go to Step 20 | Go to Step 17 | ||||||||||||||||
15 |
Is the resistance more than the specified value? | 5 ohms | Go to Step 19 | Go to Step 16 | ||||||||||||||||
16 | Measure the resistance of the low reference circuit between the boost pressure sensor and the ECM with a DMM. Is the resistance more than the specified value? | 5 ohms | Go to Step 19 | Go to Step 21 | ||||||||||||||||
17 | Test for an intermittent and for a poor connection 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 23 | Go to Step 18 | ||||||||||||||||
18 |
Is the resistance more than the specified value? | 5 ohms | Go to Step 19 | Go to Step 21 | ||||||||||||||||
19 | Repair the high resistance in the circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 23 | -- | ||||||||||||||||
20 | Replace the boost pressure sensor. Refer to Turbocharger Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 23 | -- | ||||||||||||||||
21 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 23 | -- | ||||||||||||||||
22 | Replace the turbocharger. Refer to Turbocharger Replacement in Engine Mechanical. Did you complete the replacement? | -- | Go to Step 23 | -- | ||||||||||||||||
23 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 24 | ||||||||||||||||
24 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK |