Most electrical problems are caused by poor connections. The following procedure will assist in detecting problems with connectors and with wiring. If a problem is found correct the condition and verify that the problem is resolved.
Intermittent electrical problems are sometimes resolved by disconnecting and reconnecting connectors. It is very important to check for diagnostic codes immediately before disconnecting a connector. Also check for diagnostic codes after reconnecting the connector. If the status of a diagnostic code is changed due to disconnecting and reconnecting a connector, there are several possible reasons. The likely reasons are loose terminals, improperly crimped terminals, moisture, corrosion, and inadequate mating of a connection.
Follow these guidelines:
- Always use a 1U-5804 Crimp Tool to service Deutsch HD and DT connectors. Never solder the terminals onto the wires. Refer to "SEHS9615, Servicing Deutsch HD and DT Style Connectors".
- Always use a 147-6456 Wedge Removal Tool to remove wedges from DT connectors. Never use a screwdriver to pry a wedge from a connector.
- Always use a breakout harness for a voltmeter probe or a test light. Never break the insulation of a wire in order to access to a circuit for measurements.
- If a wire is cut, always install a new terminal for the repair.
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The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere. |
Test Step 1. Check Connectors for Moisture and Corrosion
- Inspect all wiring harnesses. Ensure that the routing of the wiring harness allows the wires to enter the face of each connector at a perpendicular angle. Otherwise, the wire will deform the seal bore. Refer to Illustration 1. This will create a path for the entrance of moisture. Verify that the seals for the wires are sealing correctly.
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Illustration 2 g01131276 Diagram for the installation of a connector plug (typical example)
(1) Electronic Control Module (ECM) connector
(2) Correctly inserted plug
(3) Incorrectly inserted plug - Ensure that the sealing plugs are in place. If any of the plugs are missing, replace the plug. Ensure that the plugs are inserted correctly into the connector. Refer to Illustration 2.
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Illustration 3 g00835079 Seal for a three-pin connector (typical example) Show/hide table
Illustration 4 g01131019 Seal for a three-pin connector (typical example) Show/hide table
Illustration 5 g01131165 Seal for ECM connector (typical example) - Disconnect the suspect connector and inspect the connector seal. Ensure that the seals are in good condition. If necessary, replace the connector.
- Thoroughly inspect the connectors for evidence of moisture entry.
Note: It is normal to see some minor seal abrasion on connector seals. Minor seal abrasion will not allow the entry of moisture.
If moisture or corrosion is evident in the connector, the source of the moisture entry must be found and the source of the moisture entry must be repaired. If the source of the moisture entry is not repaired, the problem will recur. Simply drying the connector will not fix the problem. Check the following items for the possible moisture entry path:
- Missing seals
- Improperly installed seals
- Nicks in exposed insulation
- Improperly mated connectors
Moisture can also travel to a connector through the inside of a wire. If moisture is found in a connector, thoroughly check the connector's harness for damage. Also check other connectors that share the harness for moisture.
Note: The ECM is a sealed unit. If moisture is found in an ECM connector, the ECM is not the source of the moisture. Do not replace the ECM.
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| Illustration 1 | g01131211 |
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Leaky seal at the connector (typical example) | |
Expected Result:
The harness wiring, connectors, and seals are in good condition. There is no evidence of moisture in the connectors.
Results:
- OK - The harness wiring, connectors, and seals are in good condition. Proceed to Test Step 2.
- Not OK - A problem has been found with the harness or the connectors.
Repair: Repair the connectors or the wiring, as required. Ensure that all of the seals are properly in place. Ensure that the connectors have been reattached.
If corrosion is evident on the pins, sockets or the connector, use only denatured alcohol to remove the corrosion. Use a cotton swab or a soft brush to remove the corrosion.
If moisture was found in the connectors, run the engine for several minutes and check again for moisture. If moisture reappears, the moisture is wicking into the connector. Even if the moisture entry path is repaired, it may be necessary to replace the wires.
Verify that the repair eliminates the problem.
STOP
Test Step 2. Check the Wires for Damage to the Insulation
- Carefully inspect each wire for signs of abrasion, of nicks, and of cuts.
Inspect the wires for the following conditions:
- Exposed insulation
- Rubbing of a wire against the engine
- Rubbing of a wire against a sharp point
- Check all of the wiring harness fasteners in order to verify that the harness is properly secured. Also check all of the fasteners in order to verify that the harness is not compressed. Pull back the harness sleeves in order to check for a flattened portion of wire. A fastener that has been overtightened flattens the harness. This damages the wires that are inside the harness.
Expected Result:
The wires are free of abrasion, of nicks, and of cuts and the harness is properly clamped.
Results:
- OK - The harness is OK. Proceed to Test Step 3.
- Not OK - There is damage to the harness.
Repair: Repair the wires or replace the wires, as required. Verify that the repair eliminates the problem.
STOP
Test Step 3. Inspect the Connector Terminals
- Visually inspect each terminal in the connector. Verify that the terminals are not damaged. Verify that the terminals are properly aligned in the connector and verify that the terminals are properly located in the connector.
Expected Result:
The terminals are properly aligned and the terminals appear undamaged.
Results:
- OK - The terminals are OK. Proceed to Test Step 4.
- Not OK - The terminals of the connector are damaged.
Repair: Repair the terminals and/or replace the terminals, as required.
Verify that the repair eliminates the problem.
STOP
Test Step 4. Perform a Pull Test on Each Wire Terminal Connection
- Ensure that the locking wedge for the connector is installed properly. Terminals cannot be retained inside the connector if the locking wedge is not installed properly.
- Perform the
45 N (10 lb) pull test on each wire. Each terminal and each connector should easily withstand45 N (10 lb) of tension and each wire should remain in the connector body. This test checks whether the wire was properly crimped in the terminal and whether the terminal was properly inserted into the connector.
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| Illustration 6 | g01131435 |
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Receptacle lock wedge (typical example) | |
Expected Result:
Each terminal and each connector easily withstands
Results:
- OK - All terminals pass the pull test. Proceed to Test Step 5.
- Not OK - A wire has been pulled from a terminal or a terminal has been pulled from the connector.
Repair: Use the 1U-5804 Crimp Tool to replace the terminal. Replace damaged connectors, as required. Verify that the repair eliminates the problem.
STOP
Test Step 5. Check Individual Pin Retention into the Socket
- Verify that the sockets provide good retention for the pins. Insert a new pin into each socket one at a time in order to check for a good grip on the pin by the socket.
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| Illustration 7 | g01131604 |
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Diagram for testing pin retention (typical example) | |
Expected Result:
The sockets provide good retention for the new pin.
Results:
- OK - The terminals are OK. Proceed to Test Step 6.
- Not OK - Terminals are damaged.
Repair: Use the 1U-5804 Crimp Tool to replace the damaged terminals. Verify that the repair eliminates the problem.
STOP
Test Step 6. Check the Locking Mechanism of the Connectors
- Ensure that the connectors lock properly. After locking the connectors, ensure that the two halves cannot be pulled apart.
- Verify that the latch tab of the connector is properly latched. Also verify that the latch tab of the connector returns to the locked position.
Expected Result:
The connector will securely lock. The connector and the locking mechanism are without cracks or breaks.
Results:
- OK - The connectors are in good repair. Proceed to Test Step 7.
- Not OK - The connector's locking mechanism is damaged or missing.
Repair: Repair the connector or replace the connector, as required. Verify that the repair eliminates the problem.
STOP
Test Step 7. Check the Allen Head Screws on the Connectors
Visually inspect the allen head screws for the ECM connectors. Ensure that the threads on each allen head screw are not damaged.
- Connect the ECM connectors.
- Torque the allen head bolt for the 120 pin ECM connector to
7.0 ± 0.5 N·m (60 ± 4 lb in) .Show/hide table
Illustration 9 g01132849 Allen head screw for the 70 pin ECM connector (typical example) - Torque the allen head screw for the 70 pin ECM connector to
6.0 + 1.5 - 0.5 N·m (55 + 13 - 4 lb in) .Show/hide table
Illustration 10 g01132863 Allen head screw for the 40 pin ECM connector (typical example) - Torque the allen head screw for the 40 pin ECM connector to
2.25 ± 0.25 N·m (20 ± 2 lb in) .
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Illustration 8 g01132827 Allen head screw for the 120 pin ECM connector (typical example) Show/hide table
Illustration 11 g01133047 Allen head screw for the 40 pin customer connector and the 70 pin customer connector (typical example) - Torque the allen head bolt for the 120 pin ECM connector to
- Connect the customer connector.
Torque the allen head screw for the 40 pin customer connector and the 70 pin customer connector to
2.25 ± 0.25 N·m (20 ± 2 lb in) .
Expected Result:
The ECM connector is secure and the allen head screws are properly torqued.
Results:
- OK - The ECM connectors and the customer connector is properly connected. Proceed to Test Step 8.
- Not OK - The allen head screws for the ECM connector or the customer connector is damaged.
Repair: Repair the connector or replace the connector, as required. Verify that the repair eliminates the problem.
STOP
Test Step 8. Perform the "Wiggle Test" on the Caterpillar Electronic Technician (ET)
- Select the "Wiggle Test" from the diagnostic tests on Cat ET.
- Choose the appropriate group of parameters to monitor.
- Press the "Start" button. Wiggle the wiring harness in order to reproduce intermittent problems.
If an intermittent problem exists, the status will be highlighted and an audible beep will be heard.
Expected Result:
No intermittent problems were indicated during the "Wiggle Test".
Results:
- OK - No intermittent problems were found. The harness and connectors appear to be OK. If you were sent from another procedure, return to the procedure and continue testing. If this test has resolved the problem, return the engine to service.
STOP
- Not OK - At least one intermittent problem was indicated.
Repair: Repair the harness or the connector. Verify that the repair eliminates the problem.
STOP