INTRODUCTION
If no faults were found while performing preliminary inspection procedures, proceed with self-diagnostics. If no fault codes or only pass codes are present after entering self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
Note. Scan Tester (VAG 1551) must be used to make full use of the self-diagnostic system capabilities.
HARD FAILURES
On Fox, the Digifant I electronic control unit used in California vehicles is equipped with a permanent fault memory. If a fault occurs in monitored sensors and components, they store a fault in memory.
If malfunctions are present for more than 5 seconds, they are stored as Diagnostic Trouble Codes (DTCs) and will be displayed as a permanent malfunction even though the malfunction is not occurring at the time DTCs are displayed. Malfunctions that affect oxygen sensor control can only be read accurately after a test drive of at least 5 minutes.
RETRIEVING CODES
Note. See ENTERING SELF-DIAGNOSTICS for additional scan tester operating instructions.
Fox - 1.8L Digifant I (California)
- Turn ignition on. Connect Jumper Cable (357 971 514E) to Data Link Connectors (DLC) located in center console. (Scheme 22)or 2. Black end of jumper cable attaches to Black data link connector; White end of cable attaches to White connector.
- Leave jumper cable attached for 5 seconds, until on-board diagnostic CHECK ENGINE light begins to blink. Remove jumper cable. Allow on-board diagnostic code retrieval procedure to run until Code 4444 (no faults indicated) or Code 0000 (end of output) appears. To end code retrieval procedure, reconnect jumper cable to data link connectors or turn ignition off.
- To erase fault codes, turn ignition off. Connect jumper cable and turn ignition on. Leave jumper cable attached for 5 seconds, until CHECK ENGINE light begins to blink.
- When light displays code 4444 (no faults indicated), reconnect jumper cable to data link connectors or turn ignition off to end code clearing procedure. Fault memory is now erased.
Scheme 22
ECM LOCATION
| Application | Location |
|---|---|
| Fox | Under Right Side of Dash, Behind Glove Box |
ECU/ECM LOCATION
TROUBLE CODE IDENTIFICATION
| DTC (2) (Blink) Code | System/ Affected Circuit | Possible Cause/Repair |
|---|---|---|
| 00000 (4444) | No Fault | System Okay |
| 00518 (2212) | TV Potentiometer | Open Ckt (No Signal To ECM) |
| 00522 (2312) | Coolant Temp. Sensor | Open/Short To B+ |
| 00523 (2322) | Intake Air Temp. | Open/Short (No Signal To ECM) |
| 00525 (2342) | O2 Sensor | Open Ckt (No Signal To ECM) |
| 00537 (2341) | O2 Sensor Control | (3) Control Limit Exceeded Or |
| " | " | Not Reached |
| 00552 (2323) | Airflow Sensor Potentiometer | Open Ckt (No |
| " | " | Signal To ECM) |
| 01249 (4411) | Injector Drive Ckt | Open Ckt/Defective Injectors |
| 65535 (1111) | ECM | Replace Faulty ECM |
| (1) For testing information, see appropriate PIN VOLTAGE CHART S article in this section. (2) Blink code is 4-digit malfunction indicator CHECK ENGINE light code. (3) Check for near empty fuel tank. Check for CO level (fuel mixture) not within specified range (too high or too low). Check oxygen sensor circuit for a short circuit to ground. | ||
| (1) | For testing information, see appropriate PIN VOLTAGE CHART S article in this section. |
| (2) | Blink code is 4-digit malfunction indicator CHECK ENGINE light code. |
| (3) | Check for near empty fuel tank. Check for CO level (fuel mixture) not within specified range (too high or too low). Check oxygen sensor circuit for a short circuit to ground. |
TROUBLE CODE IDENTIFICATION (FOX) (1)
- Ensure battery voltage and fuses No. 13, 23 and 25. Ensure battery, body, engine, and transmission ground connections are okay. Ensure A/C system is turned off.
- Connect Scan Tester (VAG 1551) to Data Link Connectors (DLC) located in center console. Attach Black connector first, wait for VAG SELF-DIAGNOSIS display, then connect White connector. DO NOT connect scan tester Blue connector.
- Turn ignition on. Press PRINT button to turn on printer. Indicator light on button should come on. Operate scan tester and observe display. Press "1" button to select RAPID DATA TRANSFER function.
- Press "0" and "1" buttons to select ENGINE ELECTRONICS function. Press "Q" button to enter input. Electronic Control Module (ECM) identification will be displayed on scan tester.
- If CONTROL UNIT DOES NOT ANSWER message is displayed, press HELP button to print a list of possible causes. With scan tester in RAPID DATA TRANSFER function, press right arrow button. Press "00" to "08" buttons to select desired function. See appropriate SELECTABLE FUNCTIONS table. Press "Q" button to enter input.
| Function | Ignition On |
|---|---|
| 02 | Read Fault Memory |
| 05 | Erase Fault Memory |
| 06 | End Output |
| 08 | Read Measuring Value Block |
SELECTABLE FUNCTIONS (CABRIOLET & FOX)
OUTPUT CHECK DIAGNOSIS (OUTPUT DIAGNOSTIC TEST MODE)
Note. See ENTERING SELF-DIAGNOSTICS for additional scan tester operating instructions.
This scan tester function is not available for these models.
READ MEASUREMENT & READ MEASURING (TEST) VALUE BLOCK
Note. See ENTERING SELF-DIAGNOSTICS for additional scan tester operating instructions.
- Connect Scan Tester (VAG 1551) to Data Link Connectors (DLC) located in center console. With scan tester in READ MEASURING VALUE BLOCK function, press "00" to "05" buttons to select desired display group. See «DISPLAY GROUP (FOX)»(/volkswagen/fox/g1-1987-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) table.
- When display group "00" is selected, only READ MEASUREMENT BLOCK is shown on display (the zeros do not appear on display). To switch between display groups, first press the "C" button. With READ MEASUREMENT BLOCK function completed, select END OUTPUT function on scan tester. Turn ignition off. Disconnect scan tester.
| Display Group No. & Channel No. | Display Parameters | |
|---|---|---|
| 00 | ||
| 3 | Coolant Temperature | |
| 5 | Oxygen Sensor Probe Signal | |
| 01 | ||
| 1 | Engine Speed | |
| 2 | Manifold Pressure (Airflow Sensor) | |
| 3 | Coolant Temperature | |
| 4 | Injection Time | |
| 02 | ||
| 1 | Engine Speed | |
| 2 | Intake Air Temperature | |
| 3 | Not Used | |
| 4 | Injection Time | |
| 03 | ||
| 1 | Engine Speed | |
| 2 | Coolant Temperature | |
| 3 | Not Used | |
| 4 | Injection Time | |
| 04 | ||
| 1 | Engine Speed | |
| 2 | Manifold Pressure (Engine Load) | |
| 3 | Not Used | |
| 4 | Injection Time | |
| 05 | ||
| 1 | Engine Speed | |
| 2 | Throttle Valve Potentiometer | |
| 3 | Not Used | |
| 4 | Injection Time | |
DISPLAY GROUP (FOX)
CLEARING CODES
See RETRIEVING CODES.
| Application | Location |
|---|---|
| Fox | Under Right Side of Dash, Behind Glove Box |
ECU/ECM LOCATION
SUMMARY
If no hard fault codes (only "sporadic" codes) are present, driveability symptoms exist or intermittent codes exist, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.
See also:
• DISPLAY GROUP (FOX)