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28 - DTC-Based Diagnostics / MODULE, Powertrain Control (PCM), 2.9L PCM 2 / Diagnosis and Testing
P00C0-00TRBOCHARGER-SUPERCHARGER BYPASS VALVE 2 CONTROL
CIRCUIT
For a complete TURBO CHARGER SYSTEM wiring diagram, (refer to the Wiring Information).
Theory of Operation
When the throttle plate is closed suddenly, excessive boost pressure can build up between the Turbocharger and the
Throttle Body. This can occur because the compressed air created by the Turbocharger is trapped. This results in
compressor surge which can cause compressor lag or damage the Turbocharger. The Powertrain Control Module (PCM)
detects this pressure increase from feedback provided by the Boost Pressure Sensor. The Boost Pressure Sensor
operates like a typical three wire sensor. The PCM provides a 5-Volt Supply and Sensor Return circuit to the Boost
Pressure Sensor and receives the feedback voltage on the signal circuit.
The Turbocharger Surge Valve vents the boost pressure trapped between the Turbocharger and Throttle Body when the
throttle plate is closed suddenly. During normal engine operation the Turbocharger Surge Valve is de-energized (off) and
spring loaded closed. When closed the Turbocharger is allowed to create boost pressure. The PCM energizes the
Turbocharger Surge Valve to overcome the spring pressure and open the valve. When the Surge Valve is opened the
boost pressure trapped between the Turbocharger and the Throttle Body is vented back to the inlet of the Turbocharger,
relieving the pressure and preventing compressor surge. The Turbocharger Surge Valve is controlled by the PCM using a
Low Side Driver (LSD) inside the PCM.
Typical Low Side Driver Operation and Fault Detection: This type of driver circuit is generally used for relay control,
solenoid control or a similar type of driver device. The PCM provides a ground to operate the device when switched on.
The ground could be constant or Pulse Width Modulated (PWM). The PCM also provides fault detection for the device,
wiring and internal driver. Fault detection can be done by monitoring voltage on the circuit, current draw, or a combination
of both. For diagnostic purposes the PCM uses an internal pull down diagnostic resistor connected in series and a voltage
reference (V-Ref) comparator for fault detection:
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Circuit Open and Circuit Low Detection: The PCM monitors for an open circuit and short to ground when the
driver is switched off. When switched off, the available voltage passes through the device and the internal pull
down resistor connected in series. The voltage at the comparator circuit should be close to Battery voltage since
the majority of the voltage drop occurs through the diagnostic resistor. If the available voltage is less than the V-Ref,
a fault is set. In this scenario the V-Ref would be slightly below Battery voltage. An alternative method of fault
detection for an open or short to ground that is used is to monitor current draw when the internal driver is
switched on. If the module does not detect any current draw it determines that the component or circuitry is open.
Excessive current draw detected would indicate a short to ground.
Circuit High Detection: The PCM monitors for a short to voltage when the driver is switched on. When the driver
is switched on providing a path to ground through the transistor, the available voltage should be pulled low, near
zero volts since the comparator circuit is monitoring the ground side of the device. If the voltage is greater than V-
Ref, a fault is detected. In this scenario V-Ref would be slightly above zero volts.
NOTE: A load that has a resistance that is below manufacturer specification, or a second load device shorted to the low
side driver circuit can cause excessive current draw on the internal driver. The driver will be switched off to
protect against overheating and damaging the driver. In this instance the Circuit High fault may be detected
because the available voltage on the comparator circuit is above V-Ref.
When Monitored and Set Conditions
When Monitored: This diagnostic runs continuously when the following conditions are met:
Battery voltage above 9.0 volts.
With the engine running.
Turbocharger Surge Valve 2 commanded off (closed).
Set Conditions:
The PCM-2 detects an open on the Turbocharger Surge Valve 2 Control circuit for 1.5 seconds.
Default Actions:
MIL light will illuminate.
Possible Causes
FUSED ASD RELAY OUTPUT CIRCUIT OPEN/HIGH RESISTANCE
TURBOCHARGER SURGE VALVE 2 CONTROL CIRCUIT OPEN/HIGH RESISTANCE
TURBOCHARGER SURGE VALVE 2
POWERTRAIN CONTROL MODULE 2 (PCM-2)
Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding. (Refer to 28 - DTC-
Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
Diagnostic Test
1. CHECK FOR AN ACTIVE DTC
1. Turn the ignition on.
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2. With the scan tool, erase DTCs in the PCM.
3. Start the engine and test drive the vehicle. Perform several acceleration and deceleration events during the test drive.
4. With the scan tool, read DTCs and record on the repair order.
Is the DTC active or pending?
Yes
Go To 2
No
Perform the INTERMITTENT DTC diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE,
Powertrain Control (PCM) - Standard Procedure).
2. CHECK FOR OTHER DTCS
1. Refer to the recorded DTCs.
Are there any system voltage DTCs active or pending?
Yes
Perform the applicable diagnostic procedure(s). (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain
Control (PCM) /Diagnosis and Testing).
No
Go To 3
3. CHECK THE (F342) FUSED ASD RELAY OUTPUT CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the Turbocharger Surge Valve 2 harness connector.
3. Turn the ignition on.
4. Using a 12-volt test light connected to ground, probe the (F342) Fused ASD Relay Output circuit at the Turbocharger
Surge Valve 2 harness connector.
NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to
the battery.
Is the test light illuminated and bright?
Yes
Go To 4
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No
Repair the (F342) Fused ASD Relay Output circuit for an open or high resistance.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain
Control (PCM) - Standard Procedure).
4. CHECK THE (N639) TURBOCHARGER SURGE VALVE 2 CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the PCM C2 harness connector.
3. Measure the resistance of the (N639) Turbocharger Surge Valve 2 Control circuit between the Turbocharger Surge
Valve 2 harness connector and the PCM C2 harness connector.
Is the resistance below 3.0 Ohms?
Yes
Go To 5
No
Repair the (N639) Turbocharger Surge Valve 2 Control circuit for an open or high resistance.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain
Control (PCM) - Standard Procedure).
5. CHECK THE TURBOCHARGER SURGE VALVE 2 CONTROL CIRCUIT OPERATION
1. Reconnect the PCM C2 harness connector.
2. Turn the ignition on.
3. With the scan tool, actuate the Turbocharger Surge Valve 2 to 100%.
4. Using a 12-volt test light connected to 12 volts, probe the (N639) Turbocharger Surge Valve 2 Control circuit in
Turbocharger Surge Valve 2 harness connector.
NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to
the battery.
NOTE: Be certain the actuation is active when checking the circuit.
5. With the scan tool, actuate the Turbocharger Surge Valve 2 to 0%.
6. Using a 12-volt test light connected to 12 volts, probe the (N639) Turbocharger Surge Valve 2 Control circuit at the
Turbocharger Surge Valve 2 harness connector.
NOTE: The test light should not be illuminated.
Is the test light illuminated and bright with the actuation at 100% and not illuminated with the actuation at 0%?
Yes
Replace the Turbocharger Surge Valve 2 in accordance with the Service Information.
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Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain
Control (PCM) - Standard Procedure).
No
Go To 6
6. CHECK RELATED HARNESS CONNECTIONS
1. Disconnect all PCM-2 harness connectors.
2. Disconnect all related in-line harness connections (if equipped).
3. Disconnect the related component harness connectors.
4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
Proper connector installation.
Damaged connector locks.
Corrosion.
Other signs of water intrusion.
Weather seal damage (if equipped).
Bent terminals.
Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
Terminals that have been pushed back into the connector cavity.
Check for spread terminals and verify proper terminal tension.
Repair any conditions that are found.
5. Connect all PCM-2 harness connectors. Be certain that all harness connectors are fully seated and the connector
locks are fully engaged.
6. Connect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector
locks are fully engaged.
7. Connect all related component harness connectors. Be certain that all connectors are fully seated and the connector
locks are fully engaged.
8. With the scan tool, erase DTCs.
9. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
10. With the scan tool, read DTCs.
Did the DTC return?
Yes
Replace and program the Powertrain Control Module 2 (PCM-2) in accordance with the Service Information. (Refer
to 08 - Electrical/8E - Electronic Control Modules/MODULE, Powertrain Control/Removal and Installation) .
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain
Control (PCM) - Standard Procedure).
No
The wiring or poor connection problem has been repaired.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain
Control (PCM) - Standard Procedure).
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