3500B Industrial Engines with the ADEM 3 Electronic Control Module Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the starting system or if one of the diagnostic codes in Table 1 is active.

The ECM receives two input signals from the start/run/stop switch. When both of the input signals are high or open, the ECM assumes that the start/run/stop switch is in the STOP position. When both of the input signals are low or shorted to the digital return terminal, the ECM assumes that the start/run/stop switch is in the START position. After the start/run/stop switch is turned to the START position, the ECM will initiate the starting sequence. The ECM will energize the prelube system if the prelube system is available and activated. After the prelube cycle is completed the ECM will energize the start relays.

The ECM has the ability to crank the engine when the circuit for the start/run/stop switch is activated. The crank cycle will continue for the time that is equal to the cycle crank time that has been programmed or the crank cycle will continue until the engine speed reaches the crank terminate speed. If crank terminate speed is not reached in the time that is equal to the cycle crank time, the starting motor will deactivate for a time that is equal to the cycle crank time.

This process will repeat for a programmed amount of times (Total Number of Crank Cycles). If the engine does not start the starter mode on the Caterpillar Electronic Technician (ET) will display "OVERCRANK". The engine control will be in an idle state.

Illustration 1	g01268846
Typical schematic

Illustration 2	g01268849
P1 ECM connector (P1-5) Digital return (P1-21) Start/Run/Stop input 1 (P1-22) Start/Run/Stop input 2

Illustration 3	g01269000
P2 ECM connector (P2-6) Crank relay

Illustration 4	g01268992
Machine interface connector (Terminal 03) Crank relay (Terminal 09) Digital return (Terminal 37) Start signal

Illustration 5	g01234146
Location of ECM connectors

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.

2. Turn the breaker for the ECM to the OFF position.

3. Thoroughly inspect the ECM connectors. Inspect all of the other connectors for the circuit. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.

4. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

5. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.

6. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

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

Results:

• OK - The connectors and wiring are OK. Proceed to Test Step 2.

• Not OK - There is a problem in the connectors and/or wiring.

  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. Check for Active Diagnostic Codes for the Start Relay

1. Connect Cat ET to the service tool connector.

2. Turn the breaker for the ECM to the ON position.

3. Turn the switch that provides power to the keyswitch input for the ECM to the ON position.

4. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relays.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

5. Turn the start/run/stop switch to the START position.

6. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relays.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

Expected Result:

No diagnostic codes are active.

Results:

• OK - No diagnostic codes are active, but a problem is suspected in the starting system. Proceed to Test Step 6.

• Not OK - A -6 diagnostic code is active at this time. Proceed to Test Step 3.

• Not OK - A -5 diagnostic code is active at this time. Proceed to Test Step 4.

Test Step 3. Create an Open at the Start Relays

1. Turn the start/run/stop switch to the STOP position.

2. Disconnect the wires from terminal 3 on the start relays. Ensure that the wires are isolated from engine ground and other sources of electrical power.

3. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relays.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active. Check for an active diagnostic code for the start relay.

4. Turn the start/run/stop switch to the START position.

5. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relay.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active. Check for an active diagnostic code for the start relays.

6. Turn the start/run/stop switch to the STOP position.

Expected Result:

A -5 diagnostic code is now active for the start relays.

Results:

• OK - A -6 diagnostic code was active before disconnecting the wire. A -5 diagnostic code became active after disconnecting the wires. The harness and the ECM are OK. The problem may be in the start relays.

  Repair: Check for a short or an open across the coil of the start relay. The coil resistance is approximately 25 to 30 Ohms. If the resistance is incorrect, install a new start relay.

  STOP

• Not OK - A -6 diagnostic code remains active. There is a short between the start relay and the ECM. Leave the wires for the start relays disconnected. Proceed to Test Step 5.

Test Step 4. Create a Short at the Start Relays

1. Turn the start/run/stop switch to the STOP position.

2. Install a jumper wire between terminal 4 and terminal 3 at the start relays.

3. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relays.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active. Check for an active diagnostic code for the start relays.

4. Turn the start/run/stop switch to the START position.

5. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relays.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active. Check for an active diagnostic code for the start relays.

6. Turn the start/run/stop switch to the STOP position.

Expected Result:

A -6 diagnostic code is active when the jumper wire is installed. A -5 diagnostic code is active when the jumper wire is removed.

Results:

• OK - A -6 diagnostic code is active when the jumper wire is installed. A -5 diagnostic code is active when the jumper wire is removed. The engine harness and the ECM are OK.

  Repair: Check wire 229-BK for continuity between the start relays and the −Battery. If wire 229-BK is OK, check for a short or for an open across the coil of the start relay. The coil resistance is approximately 25 to 30 Ohms. If the resistance is incorrect, install a new start relay.

  STOP

• Not OK - The -5 diagnostic code remains active with the jumper in place. The open circuit is between the ECM and the start relay. Proceed to Test Step 5.

Test Step 5. Test the Operation of the ECM

1. Fabricate a jumper wire that can be used to replace the wire in the ECM connector for the start relay. Crimp a connector socket to one end of the jumper wire.

2. Disconnect the P2 ECM connector.

3. Remove the wire for the start relay from the ECM connector.

4. Install the jumper wire into the terminal location for the start relay at the ECM connector.

5. Connect the ECM connector.

6. Check the operation of the ECM by creating an open at the ECM:

   1. Hold the loose end of the jumper wire away from any components in order to create an open circuit condition.

   2. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relay.

      Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

   3. Turn the start/run/stop switch to the START position.

   4. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relay.

      Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

   5. Turn the start/run/stop switch to the STOP position.

7. Check the operation of the ECM by creating a short circuit at the ECM:

   1. Short the jumper wire to engine ground.

   2. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relay.

      Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

   3. Turn the start/run/stop switch to the START position.

   4. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the start relay.

      Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

8. Turn the start/run/stop switch to the STOP position. Return all wires to the original configuration.

Expected Result:

A -5 diagnostic code is active when the wire jumper for the start relay is open at the ECM connector. A -6 diagnostic code is active if the wire jumper for the start relay is shorted to engine ground at the ECM connector.

Results:

• OK - The ECM is operating properly. The problem is in the wiring between the ECM and the start relay. Inspect the machine interface connector for damage or for a loose, corroded connection.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

• Not OK - One of the following conditions exists: The -5 diagnostic code is not active when the wire jumper for the start relay is disconnected. The -6 diagnostic code is not active when the wire jumper is grounded to engine ground.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

  STOP

Test Step 6. Check the Start/Run/Stop Switch

1. Turn the breaker for the ECM to the ON position.

2. Turn the switch that provides power to the keyswitch input for the ECM to the ON position.

3. Monitor the status of the start/run/stop switch on Cat ET.

4. Turn the start/run/stop switch to the START position.

Expected Result:

The status of the start/run/stop switch is OFF when the start/run/stop switch is in the STOP position. The status of the start/run/stop switch is ON when the start/run/stop switch is in the START position.

Results:

• OK - The circuit for the start/run/stop switch is OK. Proceed to Test Step 8.

• Not OK - The circuit for the start/run/stop switch is not OK. The status of the start/run/stop switch is not changing on Cat ET. Proceed to Test Step 7.

Test Step 7. Check the Start/Run/Stop Switch

1. Turn the breaker for the ECM to the OFF position.

2. Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.

3. Disconnect the P1 ECM connector.

4. Turn the start/run/stop switch to the STOP position.

   1. Measure the resistance between P1-05 and P1-21 on ECM connector P1.

   2. Measure the resistance between P1-05 and P1-22 on ECM connector P1.

5. Turn the start/run/stop switch to the START position.

   1. Measure the resistance between P1-05 and P1-21 on ECM connector P1.

   2. Measure the resistance between P1-05 and P1-22 on ECM connector P1.

6. Restore the wiring to the original configuration.

Expected Result:

The resistance measurement indicates an open circuit when the start/run/stop switch is in the STOP position. The resistance measurement indicates a short circuit when the start/run/stop switch is in the START position.

Results:

• OK - The resistance measurements are OK.

  Repair: Recheck the status for the start/run/stop switch on Cat ET. If the ECM is not reading the input from the start/run/stop switch correctly, replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP

• Not OK - The resistance measurements are not OK.

  Repair: Check continuity of the wires and connectors between the start/run/stop switch and the ECM. Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the problem is no longer present. If necessary, replace the start/run/stop switch.

  STOP

Test Step 8. Check the Voltage from the Start Relays to the Start Solenoids

1. Remove the wires from terminal 2 of the start relays.

2. Turn the start/run/stop switch to the START position.

3. Measure the voltage between terminal 2 on the start relays and engine ground.

4. Turn the start/run/stop switch to the STOP position.

5. Restore the wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 9.

• Not OK - The voltage does not measure 24 ± 3 VDC.

  Repair: Measure the voltage between terminal 1 on the start relays and engine ground. If voltage is present on terminal 1 on the start relays, verify that the wire on terminal 4 on the start relays has continuity to the −Battery. If the wire on terminal 4 is OK, replace the suspect start relay.If the wire from the start relays to the −Battery is not OK, repair the wire.If voltage is not present on terminal 1 on the start relays, repair the wire between the start relays and the +Battery or repair the circuit protection between the battery and the start relays.

  STOP

Test Step 9. Check the Voltage at the Start Solenoids

1. Remove the wires from the start solenoids.

2. Turn the start/run/stop switch to the START position.

3. Measure the voltage between the wires at the start solenoid and engine ground.

4. Turn the start/run/stop switch to the STOP position.

5. Restore the wiring to the original configuration.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC.

  Repair: Install a new start solenoid.

  STOP

• Not OK - The voltage does not measure 24 ± 3 VDC. The problem is in the wiring between the start relays and the start solenoids.

  Repair: Verify that you have continuity on the return wire for the start solenoids between the start solenoids and the −Battery. If the return wire for the start solenoid is OK, repair the wire between the start solenoids and the start relays.

  STOP