C7.1 Engines and Generator Sets Caterpillar

Most electrical faults are caused by poor connections. The following procedure will help in detecting faults with connectors and with wiring. If a fault is found, correct the condition and verify that the fault is resolved.

Intermittent electrical faults are sometimes resolved by disconnecting and reconnecting connectors. 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 151-6320 Removal Tool to remove the pins from the P1/P2 connectors.

• Always use a 1U-5804 Crimp Tool to service Deutsch HD and DT connectors. Never solder the terminals onto the wires. Refer to Special Instruction, SEHS9615, "Servicing Deutsch HD and DT Style Connectors".

• Always use a 147-6456 Removal Tool to remove wedges from DT connectors. Never use a screwdriver to pry a wedge from a connector.

• Always use a 1U-5804 Crimp Tool to service AMP seal connectors. Refer to Special Instruction, REHS2556, "AMPSEAL 16 Connector System".

• Refer to Troubleshooting, "ECM Harness Connector Terminals" to service the connectors for the Electronic Control Module (ECM).

• Always use a breakout harness for a voltmeter probe or a test light. Never break the insulation of a wire to access 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.

Illustration 1	g01131276
Diagram for the installation of a connector plug (typical example) (1) ECM connector (2) Correctly inserted plug (3) Incorrectly inserted plug

Illustration 2	g01131019
Seal for a three-pin connector (typical example)

Illustration 3	g01883953
Leaky seal at the connector (typical example) Some components are not shown for clarity. (1) Wire pulled to one side. Note the gap between the seal and the wire.

Table 1

Troubleshooting Test Steps	Values	Results
1. Check Connectors for Moisture and Corrosion A. Inspect all the 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. This situation can create a path for the entrance of moisture. Verify that the seals for the wires are sealing correctly. B. 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 1. C. Disconnect the suspect connector and inspect the connector seal. Ensure that the seal is in good condition. If necessary, replace the connector. D. Thoroughly inspect the connectors for evidence of moisture entry. Note: Some minor seal abrasion on connector seals is normal. 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 repaired. If the source of the moisture entry is not repaired, the fault will recur. Simply drying the connector will not rectify the fault. Check the following items for the possible moisture entry path: · Missing seals · Incorrectly installed seals · Nicks in exposed insulation · Improperly mated connectors Moisture can also travel to a connector inside a wire. If moisture is found in a connector, thoroughly check the connector 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. E. Check the connectors for white deposits. White deposits may indicate that the connector has been contaminated with Diesel Exhaust Fluid (DEF). DEF may corrode the copper wire in the wiring harness.	Harness, connectors, and seals are OK.	Result: A fault has been found with the harness or the connectors. Repair: Repair the connectors or the wiring, as required. Ensure that all the seals are correctly installed. 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, replacement of the wires may be necessary. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: The harness, connectors, and seals are in good condition. Proceed to Test Step 2.
2. Check the Wires for Damage to the Insulation A. Carefully inspect each wire for signs of abrasion, nicks, and cuts. Inspect the wires for the following conditions: · Exposed insulation · Rubbing of a wire against the engine · Rubbing of a wire against a sharp edge B. Check all the fasteners for the harness and the strain relief components on the ECM to verify that the harness is correctly secured. Also check all the fasteners to verify that the harness is not compressed. Pull back the harness sleeves to check for a flattened portion of wire. A fastener that has been overtightened flattens the harness. This condition damages the wires that are inside the harness.	The wiring is OK	Result: There is damage to the harness. Repair: Replace the harness. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: The wires are free of abrasion, nicks, and cuts and the harness is correctly clamped. Proceed to Test Step 3.
3. Inspect the Connector Terminals Note: The ECM connectors cannot be repaired. If damage is found on an ECM connector, the harness must be replaced. A. Visually inspect each terminal in the connector. Verify that the terminals are not damaged. Verify that the terminals are correctly aligned in the connector and verify that the terminals are correctly located in the connector.	Terminals are aligned and undamaged	Result: The terminals of the connector are damaged. Repair: Repair the terminals and/or replace the terminals, as required. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: The terminals are OK. Proceed to Test Step 4.

Illustration 4	g01802454
A typical example of the lock wedge. (1) Lock wedge

Illustration 5	g02022414
Checking pin retention in an ECM connector

Table 2

Troubleshooting Test Steps	Values	Results
4. Perform a Pull Test on Each Wire Terminal Connection A. Ensure that the locking wedge for the connector is installed correctly. Terminals cannot be retained inside the connector if the locking wedge is not installed correctly. B. Perform the 45 N (10 lb) pull test on each wire. Each terminal and each connector should easily withstand 45 N (10 lb) of tension and each wire should remain in the connector body. This test checks whether the wire was correctly crimped in the terminal and whether the terminal was correctly inserted into the connector.	Pull test OK	Result: A wire has been pulled from a terminal or a terminal has been pulled from the connector in the 45 N (10 lb) pull test. Repair: Use the 1U-5804 Crimp Tool to replace the terminal. Replace damaged connectors, as required. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: All terminals pass the pull test. Proceed to Test Step 5.
5. Check the Locking Mechanism of the Connectors A. Ensure that the connectors lock correctly. After locking the connectors, ensure that the two halves cannot be pulled apart. B. Verify that the latch tab of the connector is correctly latched. Also verify that the latch tab of the connector returns to the locked position.	The connectors are locked and are not damaged	Result: The locking mechanism for the connector is damaged or missing. Repair: Repair the connector or replace the connector, as required. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: The connectors are in good condition. Proceed to Test Step 6.
6. Check the Screws on the ECM Connectors A. Visually inspect the screws for the ECM connectors. Ensure that the threads on each screw are not damaged. B. Connect the ECM connectors. C. Use a 7 mm screw to retain each of the ECM connectors. D. Tighten the two screws for the ECM connector to the correct torque of 6.0 N·m (53 lb in).	The ECM connectors are secure.	Result: The screws for the ECM connectors are damaged or a threaded hole in the ECM is damaged. Repair: Repair the connectors or replace the connectors or screws, as required. If a threaded hole in the ECM is damaged, replace the ECM. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: The ECM connectors are secured. Proceed to Test Step 7.
7. Perform the "Wiggle Test" on the Electronic Service Tool A. Select the "Wiggle Test" from the diagnostic tests on the electronic service tool. B. Choose the appropriate group of parameters to monitor. C. Press the "Start" button. Wiggle the wiring harness to reproduce intermittent faults. If an intermittent fault exists, the status will be highlighted and an audible beep will be heard.	Intermittent faults were indicated.	Result: No intermittent faults were found. If directed here from another procedure, return to the procedure and continue testing. If this test confirms that the fault has been eliminated, return the engine to service. Result: At least one intermittent fault was indicated. Repair: Repair the harness or the connector. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault.