Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engine's Electronic Control Module (ECM) or if any one of the diagnostic codes or the event code in Table 1 is active or easily repeated. Refer to Troubleshooting, "Event Codes" for information about event codes and the default trip points for these codes. You must access the monitoring system on Caterpillar Electronic Technician (ET) in order to view the current trip points for these codes.
| Diagnostic Codes Table | ||
|---|---|---|
| Code and Description | Conditions which Generate this Code | System Response |
| E043(1) Low System Voltage Warning | The battery supply voltage is less than 20 VDC for ten seconds. | The code is logged. |
| 168-0 Electrical System Voltage : High | The battery supply voltage is greater than 32 VDC for 0.5 seconds.
The engine is not being cranked. |
|
| 168-1 Electrical System Voltage : Low | The battery supply voltage is less than 18 VDC for 0.5 seconds.
The engine is not being cranked. |
|
| 168-2 Electrical System Voltage : Erratic, Intermittent, or Incorrect | The engine is running but not cranking. The battery supply voltage is less than 18 VDC for at least .06 seconds. Three times in the last seven seconds, the battery supply voltage was less than 18 VDC. | |
The engine has a Primary ECM and a Secondary ECM. The electrical power to the primary ECM comes through the breaker for the primary ECM and the contacts of relay "R2A". The electrical power to the secondary ECM comes through the breaker for the secondary ECM and the contacts of relay "R2". Power goes to pin P1-53 and pin P1-52 of the ECM(s). The −Battery comes through the breakers for the primary ECM and the secondary ECM. The −Battery connects to pin P1-63 and pin P1-65 of the ECM(s).
The Engine Control Switch (ECS) sends a signal to pin P1-70 on the primary ECM and to pin P1-70 on the secondary ECM when the ECS is in the following positions: REMOTE, STOP and START. When the primary ECM senses battery voltage on pin P1-70 of the primary ECM, the primary ECM will power up. When the secondary ECM senses battery voltage on pin P1-70 of the secondary ECM, the secondary ECM will power up. When the ECS is in the OFF position, voltage is not present on these inputs and the ECM(s) will power down.
If an emergency shutdown occurs, circuitry will energize relay "R2" and relay "R2A". When these two relays are energized the contacts of the relays will open. When the contacts of the relays open, battery power is removed from the ECM(s).
In order to restart the engine, the operator must correct the cause of the emergency shutdown. The Engine Control Switch (ECS) must be turned to the OFF position. This resets the electrical circuits in the circuit. In addition to turning the ECS to the OFF position, the operator must manually open the air shutoff valves before starting the engine.
The presence of two +Battery connections and two −Battery connections to the ECM reduce harness resistance. All of these connections must be complete in order to ensure proper engine operation.
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| Illustration 1 | g01321562 |
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Typical example | |
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| Illustration 2 | g01321565 |
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P1 connections for the electrical power supply circuit (P1-52) +Battery (P1-53) +Battery (P1-63) −Battery (P1-65) −Battery (P1-70) Keyswitch | |
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| Illustration 3 | g01321568 |
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Terminal locations for the following connectors A-C91/P-C2 connectors for the power distribution panel and A-C2/J-C2/J-C1 right hand cross over harness. (Terminal K) +Battery to primary ECM 150-BK(Black) (Terminal L) +Battery to primary ECM C150-BK(Black) (Terminal M) -Battery to primary ECM D229-BK(Black) (Terminal N) -Battery to primary ECM 229-BK(Black) (Terminal S) -Battery to secondary ECM A287-BK(Black) (Terminal T) -Battery to secondary ECM B287-BK(Black) (Terminal U) +Battery to secondary ECM A103-BK(Black) (Terminal V) +Battery to secondary ECM 103-BK(Black) | |
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| Illustration 4 | g01323336 |
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Terminal locations for the C-C17/F-C1/F-C2/G-C6 connectors for a LH Control panel (Terminal 14) Keyswitch 113-BK(Black) (Terminal 15) Remote keyswitch 040-BK(Black) (Terminal 16) +Battery to ECS M150-BK(Black) | |
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| Illustration 5 | g01622856 |
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Connector locations (1) A-C1/E-C2/E-C1 Right hand cross over harness (2) A-C2/J-C2/J-C1 Right hand cross over harness (3) A-C90/P-C1 Connectors for the power distribution panel (4) A-C91/P-C2 Connectors for the power distribution panel (5) A-C60 Connector for the prelube motor (6) A-C92/F-C1/F-C2/G-C6 Connectors for a RH Control panel (7) C-C22 Primary ECM connector P2 (8) C-C15 Primary ECM connector P1 (9) C-C28 Secondary ECM connector P2 (10) C-C29 Secondary ECM connector P1 (11) C-C47 Connector for the power relay panel (12) C-C17/F-C1/F-C2/G-C6 Connectors for a LH Control panel (13) C-C18/(TB-C1 customer or L-C1/L-C2 EMCP 3) connectors (14) C-C2/J-C1/J-C2 Left hand cross over harness (15) C-C1/E-C1/E-C2 Left hand cross over harness | |
Note: If a remote start switch is installed, the remote start switch must be in the LOCAL position for this test.
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the ECS to the OFF position.
- Turn the circuit breaker for the battery to the OFF position.
- Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Perform a
45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit. - Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- 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, and the harness and wiring are free of corrosion, of abrasion or of pinch points.
Results:
- OK - The connectors and wiring are OK. Proceed to Test Step 2.
- Not OK - The connectors and/or wiring need repair.
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 the Voltage to the ECM
- Disconnect the primary ECM connector J1/P1 and the secondary ECM connector J1/P1.
- Turn the circuit breaker for the battery to the ON position.
- Turn the ECS to the STOP position.
- Measure the voltage between the following pins on the primary ECM and on the secondary ECM.
- P1-52 and P1-63
- P1-53 and P1-65
- P1-70 and P1-65
Expected Result:
The voltage measures 24 ± 3 VDC. The difference between the three voltage measurements is less than 0.5 VDC.
Results:
- OK - The ECM is receiving the correct battery voltage.
Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- Not OK - The voltage is incorrect at all of the connections to the ECM(s). The wiring or components between the battery and the ECM are preventing the voltage from reaching the ECM. Proceed to Test Step 3.
- Not OK - P1-70 - The voltage is not 24 ± 3 VDC on the input for the keyswitch to the ECM. Proceed to Test Step 6.
Test Step 3. Check the Battery Voltage
- Turn the ECS to the OFF position.
- Turn the circuit breaker for the battery to the OFF position.
- Measure no-load battery voltage at the battery terminals. Refer to Testing and Adjusting, "Test Tools for the Electrical System" for the proper procedures to check the batteries.
- Load test the batteries. Use the 4C-4911 Battery Load Tester. Refer to the Operating Manual, SEHS9249. Refer to Special Instruction, SEHS7633.
Expected Result:
The no-load voltage at the batteries is at least 23.5 VDC and the batteries pass the load test.
Results:
- OK - The no-load voltage at the batteries is at least 23.5 VDC, and the batteries pass the load test. Proceed to Test Step 4.
- Not OK - The no-load voltage at the batteries is less than 23.5 VDC, and/or the batteries fail the load test.
Repair: The batteries or the alternator are causing the problem. Recharge the batteries or replace the batteries. Refer to Systems Operation/Testing and Adjusting.
STOP
Test Step 4. Check the Voltage from the Power Distribution Panel
- Disconnect the P-C2/A-C91 connector on the RH rigid rail.
- Measure the voltage between the following terminals on the P-C2 connector.
- Terminal S and Terminal L
- Terminal T and Terminal K
- Terminal M and Terminal U
- Terminal N and Terminal V
- Turn the ECS to the OFF position.
- Turn the circuit breaker for the battery to the OFF position.
Expected Result:
The voltage measures 24 ± 3 VDC.
Results:
- OK - The voltage measures 24 ± 3 VDC.
Repair: Check continuity of the wiring between connector A-C91 and the ECM connectors. Check for opens in the wiring and for shorts in the wiring. Refer to Illustration 1 for the connectors and terminals that interconnect the two connectors. Repair the wiring and/or connectors.
STOP
- Not OK - The voltage does not measure 24 ± 3 VDC. Verify that the wiring to the −Battery does not have an open circuit. Proceed to Test Step 5.
Test Step 5. Check the Voltage at Relay "R2" and/or Relay "R2A"
- Turn the circuit breaker for the battery to the OFF position.
- Remove the wire 103-BK(Black) and the wire A103-BK(Black) from terminal 87A of relay "R2".
- Remove the wire 150-BK(Black) and the wire C150-BK(Black) from terminal 87A of relay "R2A".
- Turn the circuit breaker for the battery to the ON position.
- Measure the voltage between the following terminals on relay "R2" and relay "R2A".
- Terminal 30 and the −Battery terminal
- Terminal 87A and the −Battery terminal
Expected Result:
The voltage measures 24 ± 3 VDC on all terminals.
Results:
- OK - The voltage is 24 ± 3 VDC.
Repair: Repair the wiring between relay "R2" and/or relay "R2A" and the P-C2 connector on the RH rigid rail.
STOP
- Not OK - The voltage is not 24 ± 3 VDC on terminal 30 of relay "R2" and/or relay "R2A".
Repair: Verify that voltage is present on wire A150 at the breaker for the primary ECM. If voltage is present at the breaker, repair the wiring between the breaker for the primary ECM and relay "R2A".
Verify that voltage is present on wire B103 at the breaker for the secondary ECM. If voltage is present at the breaker, repair the wiring between the breaker for the secondary ECM and relay "R2".
STOP
- Not OK - The voltage is not 24 ± 3 VDC on terminal 87A of relay "R2" and/or relay "R2A".
Repair: Verify that voltage is not present on wire T120 at the coil of relay "R2A". If voltage is present on wire T120, check all emergency stop switches for proper operation. Check for diagnostic codes for an engine overspeed. If voltage is not present on wire T120, replace relay "R2A".
Verify that voltage is not present on wire T120 at the coil of relay "R2". If voltage is present on wire T120, check all emergency stop switches for proper operation. Check for a diagnostic code for an engine overspeed. If voltage is not present on wire T120, replace relay "R2".
STOP
Test Step 6. Check the Voltage at the ECS
- Turn the ECS to the OFF position.
- Remove wire 113-BK(Black) from terminal 16 of the ECS.
- Turn the ECS to the STOP position.
- Measure the voltage between terminal 16 and engine ground. Measure the voltage between terminal 20 and engine ground.
Expected Result:
The voltage measures 24 ± 3 VDC on both terminals.
Results:
- OK - The voltage is 24 ± 3 VDC on both terminals.
Repair: The wire 113-BK(Black) between the ECS and the primary ECM and/or the secondary ECM needs repair. Repair the connectors or wiring and/or replace the connectors or wiring.
STOP
- Not OK - Terminal 16 - The correct voltage is not present on terminal 16 of the ECS.
Repair: If 24 ± 3 VDC is present on terminal 20 of the ECS, replace the ECS.
STOP
- Not OK - Terminal 20 - The correct voltage is not present on terminal 20 of the ECS.
Repair: Repair wire M150-BK(Black) between terminal 20 of the ECS and the ECM. Check for voltage at the connectors for the control panel. Check for voltage at diode D9. Refer to Illustration 1 for the connectors and terminals between the ECM and terminal 20 on the ECS.
STOP