Diagnostic Aids

Perform this test only when instructed during QUICK TEST or if directed by other test procedures. This test is only intended to diagnose the following:

• Wiring harness circuits (SCB, VPWR and PWR GND).
• Vacuum reservoir assembly. See Fig 1.
• Vacuum hoses/tubes.
• Supercharger (boost) by-pass solenoid (service part name is: thermactor air control solenoid/vacuum valve assembly).
• Powertrain Control Module (PCM).

Fig 1: Supercharger System Vacuum Diagram

Courtesy of FORD MOTOR CO.

1. 1) DTC P0234: Check For Other DTCs
   
   The supercharger is by-passed when brakes are on 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. If engine will not start, go to TEST A . If engine starts and then stalls, go to TROUBLE SHOOTING - NO CODES - EEC-V article and diagnose by symptom. 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. Repeat QUICK TEST  and check for DTCs. If any other DTCs are present with DTC P0234, service other DTCs before continuing with this test. If only DTC P0234 is present, go to next step.
2. 2) Check PIDs For Overboost Condition
   
   Start engine and allow to idle. Using scan tool, select IAT2, TFT and RPM PIDs from PID/DATA monitor 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 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 if TFT PID value is 275°F (135°C) or less, go to next step.
3. 3) Check Low Speed Fuel Pump Operation
   
   Start engine and allow to idle. Using scan tool, select LFPF PID from PID/DATA monitor menu. If PID value indicates a fault is present, see DIAGNOSTIC TROUBLE CODE (DTC) DEFINITIONS  and go to appropriate system test for servicing DTC P1232. If PID value does not indicate a fault is present, no problem is indicated at this time. Ensure vehicle owner has an understanding of what a brake torque condition is and that brake torque can result in transmission failure.
   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. 6) DTC P0243: Check Supercharger (Boost) By-Pass Solenoid Output
   
   Turn ignition off. Disconnect Supercharger (Boost) By-Pass (SCB) solenoid connector. Connect a test light between SCB solenoid wiring harness connector terminals. See Fig 2. Turn ignition on. Using scan tool, access OUTPUT TEST MODE. See OUTPUT TEST MODE  in ADDITIONAL SYSTEM FUNCTIONS. Command ALL ON. Observe test light and cycle scan tool start button off and on. If test light turns on then off, go to next step. If test light stays off, go to step  8). If test light stays on, go to step  11).
   Fig 2: Identifying Supercharger (Boost) By-Pass Solenoid Wiring Harness Connector Terminals

   Courtesy of FORD MOTOR CO.
5. 7) Check SCB Solenoid Resistance
   
   Turn ignition off. 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. Also check for defective vacuum reservoir. Repair as necessary. If no faults are found, go to TEST Z  and check for intermittents.
6. 8) Check For Open VPWR Circuit
   
   Measure voltage between VPWR terminal at SCB solenoid wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to next step. If voltage is not more than 10.5 volts, repair open in VPWR circuit between SCB solenoid and PCM power relay.
7. 9) Check VPWR Circuit Resistance
   
   Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 71 and VPWR terminal at SCB solenoid wiring harness connector. 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 For Open In SCB Circuit
   
   Measure resistance between PCM connector pin No. 42 and SCB terminal at SCB solenoid wiring 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 Ground
   
   Turn ignition off. Disconnect scan tool from DLC. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 41 and pins No. 51 and 103 (PWR GND). If all resistance readings are more than 10,000 ohms, go to next step. If any resistance reading is less than 10,000 ohms, SCB circuit is shorted to PWR GND circuit. Repair wiring harness as necessary.
10. 12) Check SCB Circuit Voltage
    
    Turn ignition on. measure voltage between PCM connector pin No. 41 and chassis ground. If voltage is less than one volt, replace PCM. If voltage is one volt or more, SCB circuit is shorted to VPWR or VREF circuit. Repair wiring harness as necessary.