Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
- Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
- Turn ignition on, with engine off. Using scan tool, establish communication with the AF ECM. Locate and observe the Fuel Pressure sensor data parameter. Does the Fuel Pressure sensor indicate voltage greater than 4.7 volts? If yes, go to step 4 . If no, go to next step.
- The fault is not present. See DIAGNOSTIC AIDS . Are any DTCs stored that have not been diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
- Locate and observe the Fuel Temperature sensor data parameter. Does the Fuel Temperature sensor indicate voltage greater than 4.7 volts? If yes, go to step 8 . If no, go to next step.
- Remove the fuel tank cover. Disconnect the Fuel Tank Pressure (FTP) sensor connector. Connect a fused jumper between the FTP sensor signal circuit terminal and a known-good ground. If the jumper fuse opens, repair the signal circuit shorted to battery voltage. Observe the Fuel Pressure sensor data parameter. Does the Fuel Pressure sensor indicate voltage less than 0.25 volt? If yes, go to next step. If no, go to step 9 .
- Remove jumper. Connect test leads of Digital Multimeter (DMM) between the 5-volt reference circuit terminal and sensor ground circuit terminal. Measure voltage of the 5-volt reference circuit at FTP sensor connector. Is voltage greater than 5.2 volts? If yes, go to step 10 . If no, go to next step.
- Connect the J-34142-B 12-Volt Unpowered Test Light between the sensor ground circuit terminal and battery positive. Is test light illuminated? If yes, go to step 12 . If no, go to step 11 .
- Inspect the sensor ground circuit for an open or high resistance condition between the AF ECM connector terminal and circuit splice. Inspect AF ECM connector and any in-line connectors, if applicable, for proper terminal contact. Repair wiring or terminals as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 14 .
- Inspect FTP sensor signal circuit for an open or high resistance condition between the AF ECM connector terminal and the circuit splice. Inspect the AF ECM connector and any in-line connectors, if applicable, for proper terminal contact. Inspect for a shorted condition between the FTP sensor 5-volt reference circuit and the FTP sensor signal circuit. Repair wiring or terminals as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 14 .
- Test the FTP sensor 5-volt reference circuit for a short to voltage. The FTP sensor 5-volt reference circuit is not shared with any other 5-volt reference component on the vehicle. Repair wiring as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 14 .
- Repair the open or high resistance condition of the sensor ground circuit between the FTP sensor connector terminal and the circuit splice. After repairs, go to step 15 .
- Inspect the FTP sensor connector for proper terminal contact. Repair terminal contact as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to next step.
- Replace FTP sensor. See FUEL TANK PRESSURE SENSOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. After repairs, go to step 15 .
- Replace AF ECM. See ALTERNATE FUEL ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECM with correct vehicle software and calibration. See ALTERNATE FUEL ENGINE CONTROL MODULE under PROGRAMMING. After performing repairs and procedures, go to next step.
- Using scan tool, clear the DTC information from BOTH control modules. Operate the vehicle under the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Using the scan tool parameter DTC STATUS, ensure that this DTC runs. Did this DTC RUN and PASS? If yes, system is okay. If no, go to step 2 .