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Test KJ: Supercharger By-Pass Control: Testing

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    NOTE: For additional testing information, see DIAGNOSTIC AIDS .
    NOTE: Supercharger is by-passed when brakes are applied and throttle is in wide open position. This condition causes excessive engine torque and is referred to as brake torque. If possible, check with vehicle owner to determine if engine has been subjected to a brake torque condition causing DTC P0234 to set.

  1. 1) KOEO, KOER & Continuous Memory DTC P0234: Check For Other DTCs
    DTC P0234 is set and PCM disables supercharger boost to keep from damaging engine or transmission during potentially harmful operating conditions. Possible causes are.
    • Brake Torque Condition (Brake Pedal Applied & Throttle At Wide Open Position)
    • Transmission Oil Temperature Exceeds Calibrated Threshold
    • Engine Overheating
    • Ignition Misfire Exceeding Calibrated Threshold
    • Knock Sensor Failure Or Knock Detected
    • Low Speed Fuel Pump Relay Not Switching

    If engine is a no-start, go to TEST A, step 1) . If engine starts and then stalls, diagnose by symptom. Go to SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article. If engine starts and does not stall, road test vehicle 10-15 minutes with engine speed exceeding 2000 RPM. Ensure engine is at normal operating temperature and that upper radiator hose is hot and pressurized. Repeat QUICK TEST and check for KOEO, KOER and Continuous Memory DTCs. If any other DTCs are present with DTC P0234, service other DTCs before continuing with this test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If only DTC P0234 is present, go to next step.

  2. 2) Check Scan Tool PIDs For Causes Of Overboost Condition

    Start engine and allow to idle. Using scan tool, access IAT2, TFT and RPM PIDs from PID/DATA MONITOR & RECORD menu. If IAT2 PID value is more than 230°F (110°C), check for low fluid level in intercooler system. Check for cracked intercooler lines. Repair as necessary. If TFT PID value (5.4L SC only) is more than 275°F (135°C), check for low transmission fluid level. Check for transmission leaks. Repair as necessary. If IAT2 PID value is 230°F (110°C) or less and TFT PID value is 275°F (135°C) or less, go to next step.

  3. 3) Check For Low Speed Fuel Pump Relay Not Switching

    Start engine and allow to idle. Using scan tool, access LFPF PID from PID/DATA MONITOR & RECORD menu. If LFPF PID value indicates YES (fault present), go to TEST KA, step  45) and/or  60) and perform diagnostics for DTC P1232. If LFPF PID value indicates NO (no fault present), cause of overboost condition is unable to be determined at this time. Check for engine knock while driving vehicle. Repair as necessary. If engine knock is not present, ensure vehicle owner has an understanding of a brake torque condition and that brake torque can result in transmission damage.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 6). No test procedures have been omitted.
    4. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  4. 6) For KOEO, KOER & Continuous Memory DTC P0243: Check Supercharger (Boost) By-Pass Solenoid Output
    DTC P0243 is set when PCM detects Supercharger By-pass (SCB) solenoid circuit signal exceeds minimum or maximum allowable calibrated parameters for a specified SCB solenoid duty cycle (100 percent or zero percent). Possible causes are:
    • VPWR Circuit Open To SCB Solenoid
    • SCB Solenoid Circuit Open, Or Shorted To PWR GND Or CHASSIS GND, Or VPWR
    • Faulty SCB solenoid
    • Faulty PCM

    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Disconnect SCB solenoid connector. Connect a test light between SCB and VPWR circuits at SCB solenoid harness connector. See Figure. Turn ignition switch to ON position. Using scan tool, access OUTPUT TEST MODE. See OUTPUT TEST MODE under ADDITIONAL SYSTEM FUNCTIONS. Attempt to close and open SCB solenoid driver in PCM by commanding ALL OUTPUTS ON and then OFF. Observe test light while cycling ALL OUTPUTS ON, then OFF. If test light illuminates then turns off, go to next step. If test light remains off, go to step  8). If test light remains illuminated, go to step  11).

  5. 7) Check SCB Solenoid Resistance

    Turn ignition switch to OFF position. Using a DVOM, measure resistance between SCB solenoid terminals. If resistance is not 68-78 ohms, replace SCB solenoid. If resistance is 68-78 ohms, check for damaged vacuum hoses between intake manifold and SCB solenoid. Check for vacuum reservoir leaks. Repair or replace as necessary. If no faults are found, check for intermittent faults. Go to TEST Z, step  1).

  6. 8) Check For Open VPWR Circuit Between SCB Solenoid & PCM Power Relay

    Using a DVOM, measure voltage between negative battery terminal and SCB solenoid harness connector VPWR terminal. See Figure. If voltage is more than 10.5 volts, go to step  10). If voltage is 10.5 volts or less, go to next step.

  7. 9) Check VPWR Circuit For Open In Harness

    Turn ignition switch to OFF position. Disconnect PCM connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of VPWR circuit between PCM harness connector and SCB solenoid harness connector. See PCM CONNECTOR IDENTIFICATION and Figure. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in VPWR circuit.

  8. 10) Check SCB Circuit For Open In Harness

    Using a DVOM, measure resistance of SCB circuit between PCM harness connector and SCB solenoid harness connector. If resistance is less than 5 ohms, replace PCM. If resistance is 5 ohms or more, repair open in SCB circuit.

  9. 11) Check SCB Circuit For Short To PWR GND In Harness

    Turn ignition switch to OFF position. Disconnect scan tool from DLC. Disconnect PCM connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between SCB circuit and PWR GND circuits at PCM harness connector. See PCM CONNECTOR IDENTIFICATION and Figure. See PCM PWR GND, SIG RTN & VREF TERMINAL IDENTIFICATION table. If all resistance measurements are more than 10 k/ohms, go to next step. If any resistance measurement is 10 k/ohms or less, repair short to PWR GND in SCB circuit. See WIRING DIAGRAMS .

  10. 12) Check SCB Circuit For Short To PWR Or Chassis Ground In Harness

    Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and SCB circuit at PCM harness connector. If voltage is less than one volt, replace PCM. If voltage is one volt or more, repair SCB circuit for short to VPWR, VREF or chassis ground. See WIRING DIAGRAMS .
    11. NOTE: Step  13) is performed when directed here from LACK/LOSS OF POWER symptom under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article.

  11. 13) Lack Of Power (Low Boost): Check Vacuum Hoses
    Check vacuum hoses for cracks, bends, kinks, leaks or being disconnected between the following areas:
    • Supercharger by-pass actuator and supercharger by-pass solenoid.
    • Supercharger by-pass solenoid and vacuum reservoir assembly.

    Repair or replace component(s) as necessary. If no concerns are found, return to LACK/LOSS OF POWER symptom diagnosis under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG & GASOLINE article.

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