Usage:
1. Disconnect plug P8 from receptacle J8. The locking ring helps identify P8 from J8. 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 8T8695 Adapter (nine pin breakout "T") between J8 and P8. Twist the locking rings to 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 8.
4. Pin A (+) to pin B (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 A and B and connections from J8 through the truck wiring harness back to the battery terminals for proper voltage.
5. If the voltage check between pins A and B on P8 is less than 11.0 volts with the key on, check the voltage drop from pin B of the J8 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 B. (Pin B 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 B and connections (including the battery post connections) from J8 to battery negative.
6. Pin C to pin B:
NOTE: For best accuracy, a service tool [3176 (7X1055) DDT, or (8T8697) ECAP] should be used for this test to measure the pulse width modulated signal (see Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913). If engine deceleration occurs too quickly (1.5 seconds or less), the retarder status cannot be accurately monitored by a service tool. Retarder status should then be monitored during a vehicle road test.
* The throttle must be adjusted properly (must have less than 7% throttle at low idle).
* All OEM wires and connectors to the retarder device must be connected.
* With the cruise control off and truck in neutral, increase the engine speed to high idle by depressing the throttle pedal to maximum position.
* Voltage should be 4 volts DC. 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 should be approximately 1 volt DC. (Do not depress the clutch pedal during this procedure.)
Diagnosis - Check the retarder enable circuit, using the truck wiring schematic, from Pin C (P8) to the retarder device (Jake brake or exhaust brake).
7. Pin F to Pin B:
(Equipment supplied with the engine monitoring option module).
* 1 to 4 volts DC with the key on and warning buzzer on (warning buzzer sounds for first 3 seconds).
* 12 volts DC with the warning buzzer off.
Diagnosis - If warning buzzer does not work properly, check fuses and the wire F circuitry from P8 (Pin F) through the warning buzzer back to the battery.
8. Pin G to pin B:
* 1 to 4 volts DC with the key on, check engine light on and the engine not running.
* 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 G circuitry from P8 pin G through the check engine light back to the battery.
9. Pin H to pin J:
[3176 data link to electronic dash (Fault Code 54)].
NOTE: Code 34 will flash when engine is not running. This is normal since no engine speed signal (34) is present when the key is on but the engine is not running.
* With the key on and the optional check engine switch activated, or the cruise switch off and the set/resume switch depressed to the resume position, the check engine light flashes Fault Code 54.
Diagnosis- Disconnect any optional equipment (trip recorders, etc.). If light stops flashing Fault Code 54, the fault is in the optional equipment or connection.
* Using a Deutsch wire removal tool, remove pins J and H from P8. Then, with the key on, and the optional check engine switch activated, or the cruise switch off and the set/resume switch depressed to the resume position, the check engine light does not flash Fault Code 54.
Diagnosis - Fault is in the truck harness. Check wires H and J from P8 to the dash using truck schematic. Check for an open or grounded wire. If light continues to flash Fault Code 54, the problem is in the Electronic Control Module (ECM), a Caterpillar supplied part.
10. Disconnect breakout "T" and reconnect P8 to J8. Secure locking ring.
Refer to the truck wiring schematic for additional connections at P8.