1994 PCED OBDI-A | SECTION 18A: Diesel Diagnosis — 7.3L DI Engine |
B1 CHECK VEHICLE BATTERY POWER CIRCUIT
- Key off.
- Disconnect powertrain control module (PCM). Inspect for damaged or pushed-out pins, corrosion, loose wires, etc. Service as necessary.
- Install breakout box and connect PCM to breakout box.
- Key on, engine off.
- Measure voltage between Test Pin 71/97 at the breakout box and SIG RTN circuit in the Data Link Connector (DLC). Note voltage.
- Measure voltage across battery terminals. Note voltage.
Are both voltages greater than 10.5 volts, and are both voltages within 1.0 volt of each other?
| Yes | No |
|---|
| GO to B2. | Key off, RECONNECT sensor (if applicable).
GO to A1. |
B2 CHECK VREF VOLTAGE
- Key on, engine off.
- Breakout box installed, PCM connected.
- Measure voltage between Test Pin 90 and Test Pin 91 at the breakout box.
What is the voltage?
| Greater than 6 volts | Less than 4 volts | Between 4 volts and 6 volts |
|---|
| GO to B4. | GO to B5. | GO to B3. |
B3 CHECK VREF AND SIG RTN CIRCUITS FOR CONTINUITY
- Key off.
- Sensor that sent you here disconnected.
- Breakout box installed.
- Disconnect PCM.
- Measure resistance between Test Pin 90 at breakout box and VREF circuit at vehicle harness connector of the sensor that sent you here.
- Measure resistance between Test Pin 91 at breakout box and SIG RTN circuit at vehicle harness connector of the sensor that sent you here.
Is each resistance less than 5.0 ohms?
| Yes | No |
|---|
| Reference voltage OK. REMOVE breakout box. RECONNECT all components. RERUN Scan Tool Diagnostic Test. | SERVICE open in VREF or SIG RTN circuits. REMOVE breakout box. RECONNECT all components. RERUN Scan Tool Diagnostic Test. |
B4 CHECK FOR EXCESS VOLTAGE ON VREF CIRCUIT
- Key off.
- Breakout box installed.
- Disconnect PCM.
- Disconnect STAR Tester.
Note: For proper results of this test, the STAR tester must be disconnected. Due to the circuitry of the STAR tester and the vehicle, voltage can be fed to the VREF circuit giving the false indication of a short to power.
- Key on, engine off.
- Measure voltage between Test Pin 90 at the breakout box and battery ground.
Is voltage less than 0.5 volts?
| Yes | No |
|---|
| REPLACE PCM. REMOVE breakout box. RECONNECT all components. RERUN Scan Tool Diagnostic Test. | SERVICE short to power in vehicle harness. REMOVE breakout box. RECONNECT PCM and sensor. RERUN Scan Tool Diagnostic Test. |
B5 CHECK FOR SHORTED ACCELERATOR PEDAL (AP) SENSOR
- Key off.
- Breakout box installed, PCM connected.
- Disconnect accelerator pedal (AP) sensor from vehicle harness.
- Key on, engine off.
- Measure voltage between Test Pin 90 and Test Pin 91 at the breakout box.
Is voltage less than 4.0 volts?
| Yes | No |
|---|
| Key off, RECONNECT AP sensor. GO to B6. | REPLACE AP sensor. REMOVE breakout box. RECONNECT all components. RERUN Scan Tool Diagnostic Test. |
B6 CHECK FOR SHORTED CMP SENSOR
- Key off.
- Breakout box installed, PCM connected.
- Disconnect CMP sensor.
- Key on, engine off.
- Measure voltage between Test Pin 90 and Test Pin 91 at the breakout box.
Is voltage less than 4.0 volts?
| Yes | No |
|---|
| Key off, RECONNECT CMP sensor. GO to B7. | REPLACE CMP sensor. REMOVE breakout box. RECONNECT PCM and sensors. RERUN Scan Tool Diagnostic Test. |
B7 CHECK FOR SHORTED ICP SENSOR
- Key off.
- Breakout box installed, PCM connected.
- Disconnect ICP sensor.
- Key on, engine off.
- Measure voltage between Test Pin 90 and Test Pin 91 at the breakout box.
Is voltage less than 4.0 volts?
| Yes | No |
|---|
Key off, RECONNECT ICP sensor.
GO to B8. | REPLACE ICP sensor. REMOVE breakout box. RECONNECT PCM and sensor(s). RERUN Scan Tool Diagnostic Test. |
B8 CHECK FOR SHORTED EBP SENSOR
- Key off.
- Breakout box installed, PCM connected.
- Disconnect EPB sensor.
- Key on, engine off.
- Measure voltage between Test Pin 90 and Test Pin 91 at the breakout box.
Is voltage less than 4.0 volts?
| Yes | No |
|---|
Key off, RECONNECT EBP sensor.
GO to B9. | REPLACE EBP sensor. REMOVE breakout box. RECONNECT PCM and sensor(s). RERUN Scan Tool Diagnostic Test. |
B9 CHECK FOR SHORTED MAP SENSOR
- Key off.
- Breakout box installed, PCM connected.
- Disconnect MAP sensor.
- Key on, engine off.
- Measure voltage between Test Pin 90 and Test Pin 91 at the breakout box.
Is voltage less than 4.0 volts?
| Yes | No |
|---|
Key off, RECONNECT MAP sensor.
GO to B10. | REPLACE MAP sensor. REMOVE breakout box. RECONNECT PCM and sensor(s). RERUN Scan Tool Diagnostic Test. |
B10 CHECK FOR SHORTED BARO SENSOR
- Key off.
- Breakout box installed, PCM connected.
- Disconnect BARO sensor.
- Key on, engine off.
- Measure voltage between Test Pin 90 and Test Pin 91 at the breakout box.
Is voltage less than 4.0 volts?
| Yes | No |
|---|
Key off, RECONNECT BARO sensor.
GO to B11. | REPLACE BARO sensor. REMOVE breakout box. RECONNECT PCM and sensor(s). RERUN Scan Tool Diagnostic Test. |
B11 CHECK VREF CIRCUIT FOR SHORT TO GROUND
- Key off.
- Breakout box installed.
- Disconnect PCM.
- Disconnect AP sensor.
- Disconnect MAP and BARO, if so equipped.
- Measure resistance between Test Pin 90 and Test Pins 25, 51, 76, 77, 91 and 103 at the breakout box.
Is any resistance less than 1000 ohms?
| Yes | No |
|---|
| SERVICE short to ground. REMOVE breakout box. RECONNECT all components. RERUN Scan Tool Diagnostic Test. | REPLACE PCM. REMOVE breakout box. RECONNECT all components. RERUN Scan Tool Diagnostic Test. |
B: Introduction