This procedure tests whether proper voltage is supplied to the Electronic Control Module (ECM), to the Integrated Temperature sensing Module, and to the fuel metering valve. In addition to troubleshooting diagnostic codes, use this procedure if you suspect that the ECM, the Integrated Temperature Sensing Module, or the fuel metering valve are not receiving the proper supply voltage. The cause of an intermittent power supply can occur on either the positive side or on the negative side of the power supply.
The 24 VDC power supply for the engine can be provided by a battery or by an electrical power supply. If the power is provided by an electrical power supply, the maximum allowable AC ripple is 150 mV AC peak to peak. The minimum requirement for the power supply is 22 VDC at 16 amperes. The wiring from the power supply to the component must provide a maximum voltage drop of 1.0 VDC. The power supply must be routed through a dedicated fuse or through a dedicated circuit breaker.
Terminal P1-70 ("Switched +Battery") receives battery voltage from the engine control when the control is in the START mode, in the STOP mode, or in the AUTO mode. When the ECM detects battery voltage at this input, the ECM will power up. When battery voltage is removed from this input, the ECM will power down after the engine has shut down.
The "168-02" diagnostic code indicates that the voltage of the power supply is intermittent or low while the engine is running. If the supply voltage drops to zero and stays at zero, the ECM will not log this code. The engine will shut down.
The "336-02" diagnostic code indicates that the ECM has detected a problem with the circuit for the engine control switch.
Logged diagnostic codes provide an historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.
This procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.
There are three configurations for the electrical wiring to the fuel metering valve. Verify your engine's configuration before you use this procedure.
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| Illustration 1 | g01079998 |
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Schematic for the electrical power supply | |
Test Step 1. Inspect the Electrical Connectors and Wiring
- Set the engine control to the OFF/RESET mode. Switch 16 amp circuit breaker (4) to the OFF position.
Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
- Disconnect the J1/P1 connectors. Inspect the J1 connector and the P1 connector for damage, for corrosion, and for moisture. Reconnect the J1/P1 connectors.
- Thoroughly inspect the following connections:
- Electrical connections to each of the circuit breakers
- Connectors for the 24 VDC power supply
- Connections for the engine control
- Check the torque of the allen head screw for the ECM connector. The proper torque is
6 ± 1 N·m (55 ± 9 lb in) .Show/hide table
Illustration 3 g01073509 Harness side of the P1 connector
(P1-52) +Battery
(P1-53) +Battery
(P1-55) +Battery
(P1-57) +Battery
(P1-63) −Battery
(P1-65) −Battery
(P1-67) −Battery
(P1-69) −Battery
(P1-70) Switched +Battery - Perform a
45 N (10 lb) pull test on each of the wires that are associated with the electrical power supply:- Unswitched +Battery terminals 52, 53, 55, and 57
- −Battery terminals 63, 65, 67, and 69
- Switched +Battery terminal 70
- Check the harness and wiring for abrasion and for pinch points from the power supply to the ECM and from the engine control to the ECM.
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| Illustration 2 | g01073505 |
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Terminal box (1) J1/P1 connectors for the ECM (2) J16/P16 connectors for the harness to the fuel metering valve (3) J23 connector for the service tool (4) 16 amp circuit breaker (5) 6 amp circuit breaker (6) J5/P5 connectors for the harness to the ITSM (7) J9/P9 connector for the wiring to the customer's connections | |
Expected Result:
All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.
Results:
- OK - The components are in good condition with proper connections. Proceed to Test Step 2.
- Not OK - The components are not in good condition and/or at least one connection is improper.
Repair: Perform the necessary repairs and/or replace parts, if necessary. Ensure that all of the seals are properly installed. Make sure that the connectors are properly fastened. Verify that the repair has eliminated the problem.
STOP
Test Step 2. Check the Voltage at the Power Supply and at the ECM
- Make sure that the engine will not crank during this procedure. For an engine with an electric starting motor, make sure that the battery cables are disconnected from the motor. For an engine with an air starting motor, make sure that the pressurized air supply is OFF. Make sure that the air is purged from the system.
Note: If a power supply is used instead of batteries, the minimum voltage for the power supply is 22 VDC at 16 amperes. Troubleshoot the power supply if the voltage is less than 22 VDC or more than 29 VDC.
- Measure the voltage at the terminals for the power supply. Record the voltage.
- Insert two 7X-1710 Multimeter Probes into the harness side of the P1 connector. Insert the first probe into terminal 52. Insert the second probe into terminal 63. Connect a multimeter to the probes.
- Switch the 16 amp circuit breaker ON.
- Measure the power supply voltage at the P1 connector. During the measurement, wiggle the harness in order to check for an intermittent problem. Be sure to wiggle the harness near each of the connections.
Expected Result:
The voltage that is measured at the terminals for the power supply is at least 22 VDC. The voltage that is measured at the P1 connector is within 2 VDC of the voltage that was measured at the terminals for the power supply. The voltage measurements are constant.
Results:
- OK - The ECM is receiving the correct voltage at the P1 connector.
Repair: Perform the following procedure:
Switch the 16 amp circuit breaker OFF.
Remove the probes from the P1 connector.
Proceed to Test Step 3.
- Not OK - The ECM is not receiving the correct voltage at the P1 connector.
Repair: Perform the following procedure:
- Switch the 16 amp circuit breaker OFF.
- Remove the probes from the P1 connector.
- Use a voltmeter to check the wiring. Refer to the appropriate schematic for the electrical system. Locate the source of the voltage drop.
- Make repairs, as needed.
STOP
Test Step 3. Check the Engine Control
- Make sure that the engine will not crank during this procedure. For an engine with an electric starting motor, make sure that the battery cables are disconnected from the motor. For an engine with an air starting motor, make sure that the pressurized air supply is OFF. Make sure that the air is purged from the system.
- Connect Cat ET to the service tool connector.
- Switch the 16 amp circuit breaker.
Note: An "E225 Engine Overcrank" and/or an "E233 Low Engine Prelube Pressure" event code may be generated during this step. After you have completed this step, clear the events from the "Logged Events" screen of Cat ET.
- Observe the "Active Diagnostic" screen on Cat ET and set the engine control to the STOP mode, the START mode, and the AUTO mode. Look for an active "336-02 Incorrect ECS Switch inputs" diagnostic code. Repeat this step several times.
Expected Result:
A "336-02 Incorrect ECS Switch inputs" diagnostic code was not activated when the engine control was set to the STOP mode, the START mode, and the AUTO mode.
Results:
- OK - A "336-02 Incorrect ECS Switch inputs" diagnostic code was not activated. The inputs from the engine control are correct. The problem seems to be resolved.
Repair: The problem may be intermittent. Refer to Troubleshooting, "Inspecting Electrical Connectors".
STOP
- Not OK - A "336-02 Incorrect ECS Switch inputs" diagnostic code was activated. The ECM has detected an invalid pattern for the inputs from the engine control. Proceed to Test Step 4.
Test Step 4. Check the Circuit of the Engine Control
- Make sure that the engine will not crank during this procedure. For an engine with an electric starting motor, make sure that the battery cables are disconnected from the motor. For an engine with an air starting motor, make sure that the pressurized air supply is OFF. Make sure that the air is purged from the system.
- Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
- Insert two 7X-1710 Multimeter Probes into the harness side of the P1 connector. Insert the first probe into terminal 31. Insert the second probe into terminal 61. Connect a multimeter to the probes.
- Switch the 16 amp circuit breaker ON.
Note: An "E225 Engine Overcrank" and/or an "E233 Low Engine Prelube Pressure" event code may be generated during the test. After you have completed the test, clear the events from the "Logged Events" screen of Cat ET.
Note: During these measurements, wiggle the harness in order to check for an intermittent problem. Be sure to wiggle the harness near each of the connections.
- Set the engine control to the STOP mode and measure the voltage between terminal 31 and terminal 61 of the P1 connector. The correct voltage measurement is less than one volt.
- Remove the probe from terminal 61 and insert the probe into terminal 62.
- Set the engine control to the START mode and measure the voltage between terminal 31 and terminal 62 of the P1 connector. The correct voltage measurement is less than one volt.
- Remove the probe from terminal 62 and insert the probe into terminal 64.
- Set the engine control to the AUTO mode and measure the voltage between terminal 31 and terminal 64 of the P1 connector. The correct voltage measurement is less than one volt.
- Remove the probe from terminal 31 and insert the probe into terminal 69. Remove the probe from terminal 64 and insert the probe into terminal 70.
- Set the engine control to the STOP mode and measure the voltage between terminal 69 and terminal 70 of the P1 connector. The correct voltage measurement is at least +20 VDC.
- Set the engine control to the START mode and measure the voltage between terminal 69 and terminal 70 of the P1 connector. The correct voltage measurement is at least +20 VDC.
- Set the engine control to the AUTO mode and measure the voltage between terminal 69 and terminal 70 of the P1 connector. The correct voltage measurement is at least +20 VDC.
Expected Result:
The voltage checks are within the specifications.
Results:
- OK - The voltage checks are within the specifications. Remove the probes from the P1 connector. Start the engine and run the engine. If the original problem is not resolved, the ECM may have a problem.
Repair: It is unlikely that the ECM has failed. Perform the following procedure:
Temporarily install a new ECM. Refer to Troubleshooting, "Replacing the ECM".
If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the ECM. Refer to Troubleshooting, "Replacing the ECM".
STOP
- Not OK - The P1 connector does not have the correct voltage.
Repair: Perform the following steps:
- Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
- Disconnect the wires for the STOP, START, and AUTO modes from the engine control.
- Use an ohmmeter to check the continuity of the engine control. Set the control to each mode in order to check the continuity.
- If the engine control is faulty, replace the control. If the problem is not resolved, repair the harness, when possible. Replace the harness, if necessary.
STOP