3408E and 3412E Industrial Engines Caterpillar

Use this test under the following circumstances:

• 168-00 System Voltage High

• 168-01 System Voltage Low

• 168-02 System Voltage intermittent

• Intermittent engine shutdowns

• Difficulty in starting that is not accompanied by loss of electrical accessories

Engine shutdowns that are accompanied by a loss of other electrical accessories indicate a problem in the keyswitch or in the connections to the battery terminals. This does not indicate a problem in the wiring at the ECM. Verify that there are no problems with the starting system or the charging system before you use this test.

There are two +Battery wires and there are two -Battery wires to the ECM in order to reduce resistance at the harness. The ECM continuously receives battery voltage through a 15 Amp Breaker. When the ECM senses battery voltage at the keyswitch input, the ECM turns ON. When the voltage is removed from the keyswitch input, the ECM turns OFF. The current draw from the batteries is approximately 3 Amp when the keyswitch is in the ON position and the engine is running. The current draw from the batteries is zero when the keyswitch is in the OFF position.

Illustration 1	g00896338

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF/RESET position.

2. Thoroughly inspect the J1/P1 ECM connector and the J3/P3 customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Inspect the following components for damage, corrosion, and incorrect attachment:
   • Battery posts

   • Alternator

   • Breaker

   • Engine ground

Expected Result:

All connectors, pins, and sockets should be completely inserted, and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points. All connections and grounds should be tight and free of corrosion.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Repair the circuit. Ensure that all of the seals are properly in place and that the connectors are completely coupled.Verify that the repair eliminates the problem.

  Stop.

Test Step 2. Check Battery Voltage at the Batteries

1. Turn the keyswitch to the ON position.

2. Measure the voltage at the battery posts.

Expected Result:

The voltage should be between 22 VDC and 27 VDC.

Results:

• OK - The voltage is between 22 VDC and 27 VDC. Proceed to Test Step 3.

• Not OK - The voltage is not between 22 VDC and 27 VDC.

  Repair: There is a problem with the batteries or the charging system. Refer to Testing and Adjusting, "Electrical System".

  Stop.

Test Step 3. Check the Voltage at the ECM Battery Input

Illustration 2	g00669998
J1/P1 breakout

1. Turn the keyswitch to the OFF position and install a 7X-1715 Adapter Cable (40 Pin Breakout T) at the J1/P1 ECM connector.

2. Turn the keyswitch to the ON position.

3. Measure the voltage between P1:4 (+Battery) and P1:11 (-Battery) at the breakout.

4. Measure the voltage between P1:6 (+Battery) and P1:5 (-Battery) at the breakout.

5. Connect the Caterpillar Electronic Technician (Cat ET) at the service tool connector.

6. Check for the following logged diagnostic codes in order to determine if there is an intermittent problem with the +Battery circuit to the ECM:
   • 168-00 System Voltage High

   • 168-01 System Voltage Low

   • 168-02 System Voltage intermittent

Expected Result:

The voltage should be within ± 1 VDC from the voltage at the battery posts.

Results:

• OK - Proceed to Test Step 4.

• Not OK - There is an open circuit or excessive resistance in the wiring or connections between the batteries and the ECM.

  Repair: Repair the circuit.Verify that the repair eliminates the problem.

  Stop.

Test Step 4. Check the Voltage at the ECM Keyswitch Input

Illustration 3	g00670007
J1/P1 breakout

1. Turn the keyswitch to the ON position.

2. Measure the voltage between P1:23 (Keyswitch Input) and P1:11 (-Battery) at the breakout.

Expected Result:

The voltage should be between 22 VDC and 27 VDC.

Results:

• OK - The voltage is between 22 VDC and 27 VDC. Proceed to Test Step 5.

• Not OK - The voltage is not between 22 VDC and 27 VDC. There is a problem in the wiring or the connections between the keyswitch and the ECM.

  Repair: Repair the circuit.Verify that the repair eliminates the problem.

  Stop.

Test Step 5. Check the Analog Supply Voltage at the ECM

Illustration 4	g00670062
J1/P1 breakout

1. Turn the keyswitch to the ON position.

2. Measure the voltage between P1:36 (+V Analog Supply) and P1:30 (Analog Return) at the breakout.

Expected Result:

The voltage should be between 4.5 VDC and 5.5 VDC.

Results:

• OK - The voltage is between 4.5 VDC and 5.5 VDC. Proceed to Test Step 6.

• Not OK - The voltage is not between 4.5 VDC and 5.5 VDC. Correct voltage is reaching the ECM.

  Repair: Perform the following procedure.

  1. Disconnect ECM connector P1 and carefully examine the connector for loose terminals or corroded terminals.

  2. Verify that the ECM is receiving the correct voltage from the keyswitch and from the batteries.

  3. Reconnect ECM connector P1 and repeat this Test Step.

  4. If the problem is not resolved, replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.

  Stop.

Test Step 6. Bypass the Engine Wiring Harness

Illustration 5	g00669740

Note: The bypass is ONLY FOR TESTING. The bypass may be left on the engine temporarily. REMOVE THE BYPASS BEFORE YOU RELEASE THE ENGINE TO THE CUSTOMER. The ECM will be powered if the bypass switch is activated. The keyswitch must be placed in the ON position. The bypass switch must be activated for normal engine operation. The bypass switch must be deactivated in order to shut down the engine. Deactivate the bypass switch before you perform the following connection.

Illustration 6	g00670070
ECM connector P1 (wire side)

1. Remove the wires from P1:4 (+Battery), P1:6 (+Battery), and P1:23 (Keyswitch Input).

2. Build the bypass circuit in Illustration 5.

   Note: Use black electrical tape on all temporary connections. Wrap the connections tightly. Keep the connections clean.

   1. Connect the battery end of the bypass directly to the +Battery post.

   2. Insert the sockets of the bypass into P1:4 (+Battery), P1:6 (+Battery), and P1:23 (Keyswitch Input).

   3. Install the temporary switch in the cab.

3. Operate the engine and try to duplicate the symptom.

   Note: If the symptom only occurs under certain operating conditions, test the engine under those conditions.

Expected Result:

Engine operation should be normal with the bypass in place.

Results:

• OK - There is a problem in the wiring that supplies power to the ECM or there is a problem in the wiring that supplies the signal to the keyswitch input at the ECM.

  Repair: Perform the following procedure:

  1. Remove P1:23 (Bypassed Keyswitch Input) and reinstall the 113-OR wire. If the problem returns, there is a problem in the Keyswitch Input circuit to the ECM. Repair the circuit, if necessary.

  2. If the above step is inconclusive, continue removing portions of the bypass in order to determine the specific cause of the problem. Repair the circuit, if necessary.

  3. Remove the bypass and restore all wiring to the original condition.

  Stop.

• Not OK - The intermittent problem continues.

  Repair: Remove the bypass and restore all wiring to the original condition. Refer to Troubleshooting, "Intermittent Engine Shutdowns" for further troubleshooting procedures.

  Stop.