5031766 JOHNSON *SWITCH, IGNITION

Table 1
Diagnostic Trouble Codes
CDL Code Code Description Comments
168-2 Electrical System Voltage : Erratic, Intermittent, or Incorrect The engine is running. The battery voltage falls below 6 VDC and the voltage returns above 9 VDC for three voltage readings in the last 7 seconds.
168-3 Electrical System Voltage : Voltage Above Normal The ECM detects voltage that is above the acceptable value.
168-4 Electrical System Voltage : Voltage Below Normal The ECM detects voltage that is below the acceptable value.
1834-2 Ignition Key Switch loss of signal The ECM detects an erratic signal from the keyswitch because the keyswitch was cycled at least three times in the last second The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).
Illustration 1 g02455196
Illustration 2 g02361008
Terminal locations at the P1 ECM connector that are for electrical power
(P1-48) +Battery (if applicable)
(P1-52) +Battery (if applicable)
(P1-53) +Battery (if applicable)
(P1-55) +Battery (if applicable)
(P1-57) +Battery (if applicable)
(P1-61) −Battery (if applicable)
(P1-63) −Battery (if applicable)
(P1-65) −Battery (if applicable)
(P1-67) −Battery (if applicable)
(P1-69) −Battery (if applicable)
(P1-70) Keyswitch
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Establish communication between the Cat® ET and the ECM .
B. Start the engine. Run the engine until the engine is at normal operating temperature.
C. Download the "Warranty Report" from the engine ECM before performing any troubleshooting or clearing diagnostic trouble codes.
Look for these codes:
168-2
168-3
168-4
168-2
Codes
Results: A 168-2 or a 1834-2 diagnostic code is active. - Proceed to Test Step 2.
Results: A 168-3 diagnostic code is active. - Proceed to Test Step 3.
Results: A 168-4 diagnostic code is active. - Proceed to Test Step 4.
2. Inspect the Electrical Connectors and the Wiring For the Charging Circuit
A. Turn the keyswitch to the OFF position.
B. Check the harness connections at the battery and at the alternator.
C. Check the harness between the battery and the alternator.
Electrical Connectors and Wiring
Results: The harness and connectors appear to be OK.
Repair: There is a problem with the charging system. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting".
STOP
Results: The connectors and/or wiring are not OK.
Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the repair eliminates the problem.
STOP
3. Check the Charging Circuit
A. Check the charging circuit. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting".
Charging Circuit
Results: The charging system is OK. Proceed to Test Step 4.
Results: The battery voltage is high.
Repair: here is a problem with the charging system. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting".
STOP
4. Check the Battery
A. Turn the keyswitch to the ON position. Do not start the engine.
1. Check the brightness of the lights.
B. Turn the keyswitch to the ON position. Start the engine.
1. Check the brightness of the lights.
Battery
Results: The lights are dim when the engine is not running. The lights are brighter when the engine is running. There is a problem with the battery. Proceed to Test Step 5.
Results: The lights are dim when the engine is not running. The lights are still dim when the engine is running.
Repair: There is a problem with the charging system. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting".
STOP
5. Check the Battery Charge
A. Measure the no-load battery voltage at the battery posts.
B. Load-test the batteries. Use the 4C-4911 Battery Load Tester. Refer to Special Instruction, SEHS9249, "Use of 4C-4911 Battery Load Tester for 6, 8 V and 12 V Lead Acid Batteries" and Special Instruction, SEHS7633
, "Battery Test Procedure".
Battery Charge
Results: The batteries pass the load test. The measured voltage is between 11.0 VDC and 13.5 VDC for a 12 v system. The measured voltage is between 22.0 VDC and 27.0 VDC for a 24 v system.
Repair: Check the wiring between the batteries and the ECM.
Check the connectors between the batteries and the ECM for moisture and/or corrosion.
Repair the wiring and/or the connectors.
Verify that the repair eliminates the problem.
STOP
Results: The battery voltage is low or the battery did not pass the load test.
Repair: Recharge or replace the faulty batteries. Verify that the repair eliminates the problem.
STOP