3126B and 3126E On-highway Engines Caterpillar

Use this procedure under the following situation:

Use this procedure in order to determine if the circuit for the Engine Running Output is operating properly.

The following background information is related to this procedure:

Personality Modules that have a Software Date Code dated earlier than OCT01.

The Engine Running Output is located on ECM J1/P1:13 (Output 4).

The engine running output comes on when the engine is running. The engine running output turns off when the engine rpm equals 0. This can be used to prevent the engagement of the starter motor while the engine is running. The ECM can be connected to a relay that disables the starter. The relay is normally closed so cranking can be achieved immediately at powerup. During cranking, the ECM energizes the engine running output once engine rpm reaches 50 rpm below low idle. The output is de-energized if the engine speed falls below the programmed low idle by 100 rpm. The low idle rpm is programmable. The range for low idle is between 700 rpm and 800 rpm.

Illustration 1	g00832285
Engine Running Output Circuit

Personality Modules that have a Software Date Code dated OCT01.

GMT-560 applications have a programmable parameter "Engine Running Output" that can be programmed to "P1/J1:31". If this parameter is programmed, the engine running output is located on ECM J1/P1:31 (Output 9). This feature allows the ECM to control a relay in order to prevent the starter motor from being engaged after the engine has started.

When the ignition key switch is turned to the ON position, Output 9 is low. The relay is off and the switch is closed. Current flows to the starter solenoid and this allows the starter to engage. When the engine speed reaches 600 rpm the output will go high. This energizes the relay and the switch opens. When the switch is open there is no current flow to the starter solenoid.

Illustration 2	g00832209
Engine Running Output Circuit for GMT-560

Illustration 3	g00832305
Location for the ECM terminal

Test Step 1. Inspect Electrical Connectors and Wiring.

1. Thoroughly inspect ECM vehicle harness connector J1/P1, and the firewall bulkhead connector.

   Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on terminal 13 in the ECM connector.

3. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

4. Check the harness and wiring for abrasion and for pinch points from the sensor to the ECM.

Expected Result:

All connectors, pins and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion or pinch points.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Perform the following repair:Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Use ET to Check the Relay.

1. Turn the ignition key switch to the ON position.

2. Access the special test"Engine Running Output" on ET. The "Engine Running Output" test will enable the engine running output when the test is active.

3. Begin the "Engine Running Output" test and listen for the relay to "click". You may need to be near the engine in order to hear the "click".

Expected Result:

The relay activates when the special test is enabled.

Results:

• Yes - The ECM and vehicle components are operating correctly.STOP

• No - Proceed to Test Step 3.

Test Step 3. Use ET to Check the ECM.

1. Connect ET to the cab data link connector.

2. Turn the ignition key switch to the OFF position.

3. Disconnect the ECM vehicle harness connector J1/P1.

4. Connect a breakout T between ECM connectorsJ1 and P1.

5. Connect a voltage test lamp to terminal 13 (Output 4) and terminal 65 (-battery) of the breakout T.

   Note: If the vehicle is a GM-560 application, connect the voltage test lamp to terminal 31 (Output 9) and terminal 65 (-battery) of the breakout T.

6. Turn the ignition key switch to the ON position.

7. Access the special test "Engine Running Output" on ET.

8. Cycle the special test "Engine Running Output" to "Active" and to "Not Active" and watch the voltage test lamp.

9. Stop the special test.

   Note: A multimeter can not be used in place of the voltage test lamp when the ECM outputs are being tested.

Expected Result:

The voltage test lamp turns ON when the test is active. The voltage test lamp turns OFF when the test is not active.

Results:

• Yes - The ECM is OK. The problem is in the vehicle wiring. Inspect the vehicle wiring and then repair the vehicle wiring. Otherwise, send the vehicle to the OEM dealer for repair. Verify that the original condition is resolved.STOP

• No - Temporarily connect a test ECM. Use the "Engine Running Output Special Test" on ET to check the ECM. If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the repair eliminates the problem.STOP