1996 PCED OBDI | SECTION 18: Diesel Diagnosis — 7.3L DI Engine |
AF: Unable to Activate Self Test/SCP Communication Error/DTC Not Listed | AF: Introduction |
AF1 VERIFY SELF TEST ACTIVATION METHOD USED
Was the correct procedure used?
Yes | No |
Correct procedure for activating self test was used. GO to AF2. | REFER to Scan Tool Diagnostic Test Procedures section for correct operating procedures. |
AF2 CHECK PCM OUTPUT
Note: NGS Tester will kick out if battery voltage drops below 9.5 volts. If performing repeated self testing, unplug glow plug relay to prevent the battery from going dead, disregard code 0380 while glow plug relay is unplugged. If equipped with auxiliary powertrain control system, it must be off while trying to perform self test.
- Verify that batteries are fully charged and are not the cause of the communication error.
Does engine start?
Yes | No |
GO to AF3. | GO to B1. |
AF3 CHECK B+ AT DATA LINK CONNECTOR (DLC)
- Key off.
- Inspect the DLC for damage. Service as necessary.
- Measure resistance between B+ circuit cavity at the DLC Pin 16 and B+ post.
- Key off.
Is resistance less than 5 ohms?
Yes | No |
GO to AF4. | SERVICE open in DLC B+ circuit. RERUN Quick Test. |
AF4 CHECK DLC CHASSIS GROUND CONTINUITY
- Key off.
- Measure resistance between chassis ground circuit cavity at the DLC Pin 4 and ground.
Is resistance less than 5.0 ohms?
Yes | No |
GO to AF5. | SERVICE open in DLC chassis ground circuit. RERUN Quick Test. |
AF5 CHECK DLC PWR GND CIRCUIT CONTINUITY
- Key off.
- Disconnect PCM. Inspect for damaged or pushed-out pins, loose wires, corrosion, etc. Service as necessary.
- Install breakout box, leave PCM disconnected.
- Measure resistance between Test Pin 51, 76, 77, 103 (PWR GND) at the breakout box and the PWR GND circuit cavity at the DLC Pin 5.
Is resistance less than 5.0 ohms?
Yes | No |
GO to AF6. | SERVICE open in DLC PWR GND circuit. RECONNECT the PCM. REMOVE breakout box. RERUN Quick Test. |
AF6 CHECK DLC BUS(-) CIRCUIT CONTINUITY
- Key off.
- Breakout box installed, PCM disconnected.
- Measure resistance between Test Pin 15 [BUS(-)] at the breakout box and the BUS(-) circuit at the DLC Pin 10.
Is resistance less than 5.0 ohms?
Yes | No |
GO to AF7. | SERVICE open in the DLC
BUS (-) circuit. RECONNECT the PCM. REMOVE breakout box. RERUN Quick Test. |
AF7 CHECK BUS(-) CIRCUIT FOR SHORT TO GROUND
- Key off.
- Breakout box installed, PCM disconnected.
- Measure resistance between Test Pin 15 [BUS(-)] at the breakout box and ground.
Is resistance greater than 10,000 ohms?
Yes | No |
GO to AF8. | SERVICE short to ground in the BUS(-) circuit. RECONNECT the PCM. REMOVE breakout box. RERUN Quick Test. |
AF8 CHECK BUS(-) CIRCUIT FOR SHORT TO POWER
- Key off.
- Breakout box installed, PCM disconnected.
- Key on, engine off.
- Measure voltage between Test Pin 15 [BUS(-)] and Test Pin 51/76/77 or 103 (PWR GND) at the breakout box.
Was the voltage greater than 1.0 volt?
Yes | No |
SERVICE short to power in the BUS(-) circuit. RECONNECT the PCM. REMOVE breakout box. RERUN Quick Test. | GO to AF9. |
AF9 CHECK DLC BUS(+) CIRCUIT CONTINUITY
- Key off.
- Breakout box installed, PCM disconnected.
- Measure resistance between Test Pin 16 [BUS(+)] at the breakout box and BUS(+) circuit at the DLC Pin 2.
Is resistance less than 5.0 ohms?
Yes | No |
GO to AF10. | SERVICE open in DLC BUS(+) circuit. RECONNECT the PCM. REMOVE breakout box. RERUN Quick Test. |
AF10 CHECK BUS(+) CIRCUIT FOR SHORT TO POWER
- Key off.
- Breakout box installed, PCM disconnected.
- Key on, engine off.
- Measure voltage between Test Pin 16 [BUS(+)] and Test Pins 51, 76, 77 or 103 (PWR GND) at the breakout box.
Was the voltage greater than 1.0 volt?
Yes | No |
SERVICE short to power in the BUS(+) circuit. RECONNECT the PCM. REMOVE breakout box. RERUN Quick Test. | GO to AF11. |
AF11 CHECK BUS (+) AND BUS (-) SHORTED TOGETHER
- Key off.
- Breakout box installed, PCM disconnected.
- Measure resistance from Pins 15 and 16 at the breakout box.
Is resistance greater than 10,000 ohms?
Yes | No |
REPLACE PCM. CLEAR DTCs and RETEST. | REPAIR short between BUS + and BUS - circuits. |