3126B and 3126E On-highway Engines Caterpillar

Use this procedure under the following situation:

Use the following information in order to determine if the Wait to Start Lamp is operating incorrectly.

Terminal 31 (Output 9)

The output 9 (terminal 31) can be used as a fast idle lamp or a Wait to Start Lamp output. The "Output #9" parameter defaults to "Fast Idle Lamp", but the parameter can be programmed to operate as a wait to start lamp.

Note: When the "Truck Manufacturer" is programmed to "GM" configurations the "Output #9" parameter is unavailable. The "Output #9" parameter functions as fast idle lamp output.

If the "Output #9" parameter is programmed to "Wait To Start Lamp", the ECM will turn on output 9 when the air inlet heater is operating and the engine is not running. The wait to start lamp functions similarly to the lamp for the air inlet heater that can be installed in parallel with the relay for the air inlet heater circuit. The wait to start lamp illuminates only when the engine is not running. The lamp for the air inlet heater illuminates when the relay for the air inlet heater is energized.

OCT01 Software

The parameter "Output #9" is no longer available. The parameter "Wait To Start Lamp" can be programmed to "J1/P1:31" or "None". When the parameter is programmed to "J1/P1:31" a lamp circuit can be connected to terminal 31 in order to indicate that the air inlet heater is on and the engine is not running. The parameter "Fast Idle Enabled Lamp" must be programmed to "J1/P1:21" for this feature to be used.

Note: This feature is only available when "Truck Manufacturer" is programmed to "Other".

Electrical Connection of Lamps

One terminal of the lamp must be connected to battery voltage through the vehicle wiring. The other terminal is connected to the ECM at the vehicle harness connector J1/P1 at terminal 31.

The ECM provides a path to ground in order to turn on the lamp.

Illustration 1	g00770585

Illustration 2	g00770189

Test Step 1. Inspect Electrical Connectors and Wiring.

1. Thoroughly inspect ECM vehicle harness connector J1/P1, the firewall bulkhead connector, or the wait to start lamp. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the wait to start lamp.

   Refer to Illustration 2.

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 pinch points from the battery 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: 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.

  STOP

Test Step 2. Check for Normal Operation of the Wait to Start Lamp.

1. Connect ET. Access the configuration screen and ensure that the "Output #9" parameter is programmed to "Wait To Start Lamp". For OCT01 Software, ensure that "Wait to Start Lamp" is programmed to "J1/P1:31". Also, "Fast Idle Enabled Lamp" must be programmed to "J1/P1:21".

2. Turn the ignition key switch to the OFF position for ten seconds. Turn the ignition key switch to the ON position.

3. The wait to start lamp should illuminate for approximately two seconds when the key switch is turned on. If conditions require the air inlet heater to turn on, the wait to start lamp should remain illuminated until the air inlet heater turns off or the engine is started.

Expected Result:

The wait to start lamp turns on and the wait to start lamp turns off per the above description.

Results:

• Yes - The wait to start lamp appears to operating correctly at this time.STOP

• No - Proceed to Test Step 3.

Test Step 3. Test the Circuit for the Wait to Start Lamp

Illustration 3	g00770210
Vehicle harness connector P1

1. Disconnect ECM vehicle harness connector J1/P1.

2. Fabricate a jumper wire 100 mm (4 inch) long. Crimp a Deutsch pin to both ends of the wire.

3. Insert the jumper into terminal 31 of connector P1.

4. Connect the other end of the jumper wire to terminal 65 (−battery) of connector P1.

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

6. While the lamp is being watched, insert the jumper wire and remove the jumper wire.

   Refer to Illustration 3.

Expected Result:

Result 1 The wait to start lamp turns on while the jumper is connected to both sockets. Also, the wait to start lamp turns off when the jumper is removed from one of the sockets.

Result 2 The lamp does not turn on while the jumper is connected to both sockets.

Result 3 The lamp will stay on while the ECM vehicle harness connector is disconnected.

Results:

• Result 1 - The wait to start lamp is functioning properly. Proceed to Test Step 4.

• Result 2 - The lamp did not turn on. The vehicle's lamp circuit is not functioning properly. The lamp is probably burned out or there is a problem in the wiring from the cab to either the ECM or the +Battery connection. Repair the lamp circuit or send the vehicle to the OEM dealer for repairs.STOP

• Result 3 -

  Repair: Perform the following diagnostic procedure:The circuit between the ECM and the lamp is shorted to chassis ground. Repair the circuit or send the vehicle to the OEM dealer for repairs.

  STOP

Test Step 4. Check ECM Operation of Wait to Start Lamp.

Illustration 4	g00770221
ECM breakout T-connector

1. Disconnect ECM vehicle harness connector J1/P1.

2. Insert a breakout T between ECM vehicle harness connector J1 and ECM vehicle harness connector P1.

3. Connect one probe of the voltage test lamp to terminal 65 (-battery). Connect the other probe of the voltage test lamp to terminal 52 (unswitched +battery) of the breakout T.

4. The test lamp should turn on. If the test lamp does not turn on, either the test lamp is faulty or the wiring to the ECM is faulty. Continue with this step if the lamp turns on.

5. Leave the probe of the test lamp connected to terminal 52 (unswitched +battery).

6. Connect the other probe of the test lamp to terminal 31 (output 9) of the breakout T.

   Refer to Illustration 4.

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

8. Connect ET to the cab data link connector. Access the configuration screen and ensure that the "Output #9" parameter is programmed to "Wait To Start Lamp".

9. Turn the ignition key switch to the OFF position for ten seconds. Turn the ignition key switch to the ON position.

10. The wait to start lamp should illuminate for approximately two seconds when the key switch is turned on. If conditions require the air inlet heater to turn on, the wait to start lamp should remain illuminated until the air inlet heater turns off or the engine is started.

Expected Result:

The test lamp turns on and the test lamp turns off per the above description.

Results:

• Yes - The ECM is operating correctly. There is a problem in the vehicle wiring or the lamp.STOP

• No -

  Repair: Temporarily connect a test ECM. Ensure that the "Output #9" parameter is programmed to "Wait To Start Lamp". Check the ECM operation of the PTO Switch ON Lamp when the test ECM is installed. If the problem is resolved with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM.

  STOP