Usage:
1. Disconnect plug P7 from receptacle J7. Check the connections for damaged wires or pins and corrosion. Also check that the pins are at the proper height in the connector. Check that the wires and pins are tight in the connectors by pulling (slightly) on each wire of each connector (including the breakout "T").
2. Install the 9X1160 Adapter (40-pin breakout "T") between J7 and P7 and secure the connections.
3. Connect the voltmeter as shown. Check for the appropriate voltages between the lettered "T" pins as explained in Steps 4 through 19.
4. Check system voltage.
Pin 1 (+) to pin 2 (ground) system voltage should be approximately 12 volts DC with key on (no accessories). Minimum voltage is 11.0 volts DC. While cranking the voltage should be 8 to 12 volts DC.
Diagnosis - Using the truck wiring schematic, check wires 1 and 2 and connections from J7 through the truck wiring harness back to the battery terminals for proper voltage.
5. Check voltage drop from battery.
If the voltage check between pins 1 and 2 on P7 is less than 11.0 volts with the key on, check the voltage drop from pin 2 of the J7 connector to the negative battery post while cranking. For this test, the common lead (black) should be connected to the negative battery post first. Then place the positive (red) lead into pin 2. (Pin 2 is chassis ground). Voltage should be less than .5 volts DC when cranking.
Diagnosis - If voltage drop is greater than .5 volts DC, check wire 2 and connections (including the battery post connections) from J7 to battery negative.
6. Parking Brake
Pin 11 (parking brake) to 2 (ground):
- * Less than .5 volts DC with the key on and parking brake applied.* More than 4.5 volts DC with the key on and parking brake released.
Diagnosis - Disconnect breakout "T" and check the individual switch circuits for open, ground or faulty switch. Switch circuit must have less than 10 ohms resistance and more than 20,000 ohms resistance to chassis ground.
7. Check brake switch.
Pin 30 (brake switch) to 2:
- * Less than .5 volts DC with the key on.* More than 4.5 volts DC with brake pedal applied and the key on.
Diagnosis - Disconnect breakout "T" and check the individual switch circuits for open, ground or faulty switch. Switch circuit must have less than 2.5 ohms resistance and more than 5000 ohms resistance to chassis ground.
8. Check vehicle speed buffer.
When testing for speedometer problems on trucks that have a single sensor with a single winding for vehicle speed, also follow J14 tests 6, 7 and 8.
A. Disconnect the two buffer input wires from the Vehicle Speed Sensor. Using a long jumper wire, connect the white input wire to P7 Pin 1 (+battery).
- * With key ON, engine OFF, measure voltage from P7 Pin 33 (vehicle speed) and P7 Pin 2 (-battery).* Voltage should read less than 1.0 volts DC.
B. Move the jumper from the white buffer input wire to P7 Pin 2 (-battery).
- * Measure voltage from P7 Pin 33 to P7 Pin 2.* Voltage should read between 4.5 and 8.0 volts DC.
Diagnosis: If both voltages are correct, the buffer output for the ECM is operating normally. Check that the Vehicle Speed Sensor is operating and is correctly adjusted. Follow P-504, Vehicle Speed Signal Test, in Electronic Troubleshooting, Form No. SENR5503.
If the ECM is still not receiving the signal, check the engine harness between J7 Pin 33 and P4 Pin 18 for an open or short circuit. If the harness checks OK, then the ECM is not reading the signal. Replace the ECM and recalibrate boost and speed/timing sensors.
Diagnosis: If both voltages are not correct, check for open or short circuit in the truck harness between the Vehicle Connector (P7) and the Vehicle Speed Buffer Connector (J14). If harness checks OK, go to J14 Connector Tests.
9. Check throttle position sensor.
From P7 Pin 40 (throttle) to P7 Pin 2 (-battery):
- * Less than 1.5 volts DC with key ON and pedal in low idle position.* More then 3.5 volts DC with foot pedal at maximum throttle position.
Diagnosis: Disconnect breakout "T" from J7 and check continuity from P7 Pin 40 to J11 Pin C and from P7 Pin 2 to J11 Pin B using the truck wiring schematic. Check for an open circuit, short to ground or poor connection. Proceed to J11 connector tests.
NOTE: The Throttle Position Sensor sends a Pulse Width Modulated (PWM) signal (also referred to as a "duty cycle" signal) to the ECM. The upper level of the signal is at 5.0 volts DC, and the lower level is at 0 volts DC. As the duty cycle percentage increases, the percent of the signal at 5.0 volts increases and the percent at 0 decreases.
A voltmeter tends to average out the pulses and will give a general indication that the sensor is working properly by reading higher as the duty cycle percent increases.
If there is any doubt that the Throttle Position Sensor is correctly adjusted, refer to Throttle Position Sensor Adjustment, in Electronic Troubleshooting, Form No. SENR5503 or in Systems Operation, Testing and Adjusting, Form No. SENR5508.
10. Check cruise control switch.
NOTE: Steps 10, 11, 12 and 13 can be more easily checked using the appropriate status screens of the DDT (7X6400) or ECAP (8T8697) service tools.
From P7 Pin 10 (cruise control ON/OFF) to P7 Pin 2 (-battery).
- * More than 4.5 volts DC with the cruise control switch in the off position and the key on.* Less than .5 volts DC with the cruise control switch in the on position and the key on.
Diagnosis - Disconnect breakout "T" and check the individual switch circuits for open, ground or faulty switch. Switch circuit must have less than 10 ohms resistance and more than 20,000 ohms resistance to chassis ground.
11. Check clutch switch.
Pin 31 to pin 2:
- * Less than .5 volts DC with the key on.* More than 4.5 volts DC with the clutch disengaged and the key on.
Diagnosis - Disconnect breakout "T" and check the individual switch circuits for open, ground or faulty switch. Switch circuit must have less than 10 ohms resistance and more than 20,000 ohms resistance to chassis ground.
12. Check resume/decel switch.
Pin 3 to pin 2:
- * More than 4.5 volts DC with set resume switch in the center position and the key on.* Less than .5 volts DC in resume (decelerate) position with the key on.
Diagnosis - Disconnect breakout "T" and check the individual switch circuits for open, ground or bad switch. Switch circuit must have less than 10 ohms resistance and more than 20,000 ohms resistance to chassis ground.
13. Check set/accel switch.
Pin 38 to pin 2:
- * More than 4.5 volts DC with set resume switch in the center position and the key on.* Less than .5 volts DC in set (accelerate) position with the key on.
Diagnosis - Disconnect breakout "T" and check the individual switch circuits for open, ground or faulty switch. Switch circuit must have less than 10 ohms resistance and more than 20,000 ohms resistance to chassis ground.
14. Check retarder enable circuit.
Pin 22 to pin 2:
NOTE: If engine deceleration occurs too quickly (1.5 seconds or less) the retarder status cannot be accurately monitored while stationary. Retarder status should then be monitored during a vehicle road test.
- * The throttle must be adjusted properly. The remote mounted sensor must have 15 to 20% duty cycle at low idle, 80 to 85% duty cycle at high idle and the pedal mounted sensor must have 10% to 22% at low idle and 75% to 90% at high idle.* All OEM wires and connectors to the retarder device must be connected.* With the cruise control off, truck in neutral and the clutch engaged, increase the engine speed to high idle by depressing the throttle pedal to maximum position.* Voltage should be less than .5 volts DC with engine speed steady at high idle. Quickly release the throttle and allow the engine to return to the low idle position.* During the engine deceleration from high idle to 950 rpm, voltage at pin 22 should be above 10 volts DC. (Do not depress the clutch pedal during this procedure.)
Diagnosis - Check the retarder enable circuit, using the truck wiring schematic, from Pin 22 (P7) to the retarder device (compression brake or exhaust brake).
15. Check engine light.
Pin 29 to pin 2:
- * Less than 2.0 volts DC with the key on, check engine light on and the engine not running.* More than 12 volts DC with the engine running and the check engine light off.
Diagnosis - If check engine light does not work properly, check bulb, fuses and wire 29 circuity from P7 pin 29 through the check engine light back to the battery.
NOTE: Code 55 will flash when engine is not running. This is normal since there are no detected faults (55).
16. Check coolant level sensor.
Pin 39 to pin 2:
- * 5 ± 0.4 volts DC with key on and coolant present at coolant level sensor.* 0 volts DC with key on and coolant not present at coolant level sensor.
Pin 19 to pin 2:
- * 0 volts DC with key on and coolant present at coolant level sensor.* 5 ± 0.4 volts DC with key on and coolant not present at coolant level sensor.
Diagnosis - Disconnect breakout "T" and check wires 39 and 19 circuitries from P7 pins 39 and 19 through the coolant level sensor back to the battery.
17. Check warning lamp.
Pin 12 to pin 2:
- * Less than 2.0 volts DC with the key on, warning lamp on and the engine not running.* More than 12 volts DC with the engine running and the warning lamp off.
Diagnosis - If warning lamp does not work properly, check bulb, fuses and wire 12 circuitry from P7 pin 12 through the warning light back to the battery.
NOTE: Code 55 will flash when engine is not running. This is normal since there are no detected faults (55).
18. Check wiring to optional connector J12.
This connects the 3406C (PEEC III) Data Link to the optional electronic dash connector J12.
From P7 Pin 21 (ATA data link -) to P7 Pin 32 (ATA data link +):
- * Data only is present on these wires and no voltage checks apply.* The wires from P7 Pin 21 to J12 Pin H and from P7 Pin 32 to J12 Pin J may be tested with an ohmmeter for continuity, short circuits or poor connections.
19. Restore connections.
Disconnect breakout "T" and reconnect P7 to J7.
- * If problem still exists, go to next connector in problem chart.* If this is the last connector to be checked, use the ECAP or DDT to check parameters, status screens and diagnostic codes.
Refer to the truck wiring schematic for additional connections at P7.
If additional troubleshooting is required, refer to Electronic Troubleshooting, Form No. SENR5503.