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 Starting Aid Output is operating properly.

The following background information is related to this procedure:

OCT01 Software

Starting Aid Output

Output 2 is available to connect a relay and/or a solenoid in order to control a starting aid system. The parameter "Starting Aid Output" must be programmed to "Automatic" in order to use output 2 as a starting aid output.

Typical starting aid systems inject ether into the inlet manifold in order to aid starting of the engine during cold weather operation. The output is automatically controlled by the ECM. The reading from the coolant temperature sensor is used to determine if conditions require the use of the starting aid. If a fault condition exists with the circuit for the coolant temperature sensor, the reading from the inlet manifold temperature sensor will be used. The starting aid output will be enabled for a maximum of 30 seconds while the engine is cranking and the temperature reading is below 0 °C (32 °F). The starting aid output will be disabled if the engine speed rises above 500 rpm. The starting aid output will also be disabled if a condition that prevents fuel injection occurs.

Illustration 1	g00838120
Schematic for the starting aid circuit

Test Step 1. Inspect Electrical Connectors and Wiring.

Illustration 2	g00838127
Pin locations for output 2

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 10 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. Connect ET to the cab data link connector.

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

3. Access the special test"Starting Aid Output" on ET. The "Starting Aid Output" test will enable output 2 when the test is active.

4. Begin the "Starting Aid 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.

Illustration 3	g00838135
Breakout T

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 10 (output 2) and terminal 65 (-battery) of the breakout T.

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

7. Access the special test "Starting Aid Output" on ET.

8. Cycle the special test "Starting Aid 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 "Starting Aid 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