VALVE GP-MAIN CONTROL 4988900 - Caterpillar

Illustration 9 g01439783
Terminal locations at the left rail connector for the engine speed/timing sensors
(Terminal 24) Terriary speed/timing signal (LH) (−)
(Terminal 25) Tertiary speed/timing signal (LH) (+)
(Terminal 26) Primary speed/timing signal (+)
(Terminal 27) Primary speed/timing signal (−)
Illustration 10 g01439786
Terminal locations at the right rail connector for the engine speed/timing sensors
(Terminal 62) Secondary speed/timing signal (RH) (−)
(Terminal 63) Secondary speed/timing signal (RH) (+)
Illustration 11 g02461238
Location of the covers for inspection of the camshaft thrust washer
(15) Covers
Illustration 12 g02461279
Location of the camshaft components for inspection
(16) Thrust Washer
(17) Plate
(18) Bolt
Table 5
Troubleshooting Test Steps Values Results
4. Measure the Sensor Resistance through the Engine Harness
A. Turn the keyswitch to the OFF position.
B. Disconnect the P2 connector.
C. Perform the following procedure in order to measure the resistance of the primary engine speed/timing sensor:
a. Measure the resistance from P2-25 (primary speed/timing signal (+)) to P2-35 (primary speed/timing signal (−)).
Resistance .......................... 110 to 200 Ohms
D. Perform the following procedure in order to measure the resistance of each of the secondary engine speed/timing sensors:
a. Measure the resistance from P2-46 (secondary speed/timing signal (RH) (+)) to P2-47 (secondary speed/timing signal (RH) (−)).
Resistance ....................... 1000 to 1200 Ohms
b. Measure the resistance from P2-26 (tertiary speed/timing signal (LH) (+)) to P2-36 (tertiary speed/timing signal (LH) (−)).
Resistance ....................... 1000 to 1200 Ohms
Resistance Measurements
Results: The resistance measurements are within the specifications.
Repair: The sensors and the harness are OK. There may be a problem with the ECM. Perform the following procedure:
1. Temporarily connect a test ECM.
Refer to Troubleshooting, "ECM - Replace".
2. Recheck the circuit in order to ensure that the original problem has been resolved.
If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM.
Verify that the problem is resolved.
If the problem is not resolved with the test ECM, reinstall the original ECM. Restore the wiring to the original configuration.
The electrical system for the speed/timing circuit appears to be OK. There may be a mechanical problem with the engine. Perform the following procedure:
Check the condition of the camshaft thrust washer.
1. Remove one of the covers (15) from the flywheel housing cover group in order to inspect the condition of the camshaft thrust washer.
2. Visually inspect the condition of thrust washer (16), plate (17), and three bolts (18). Check for loose bolts, loose or broken plate, and broken or worn thrust washer.
If a problem is found with the thrust washer for the camshaft, repair or replace the faulty components. Refer to the Disassembly and Assembly manual for details. Validate the repair by checking the system for the original diagnostic code
If the thrust washer and the associated components are OK, recheck the electrical system for an intermittent electrical condition.
Results: The readings are not within the specifications. The sensor resistance is not within the acceptable range when the sensor resistance is measured through the engine harness.
Proceed to Test Step 5.
Illustration 13 g01155187
Harness connector for the engine speed/timing sensors
(Terminal 1) Signal (−)
(Terminal 2) Signal (+)
Table 6
Troubleshooting Test Steps Values Results
5.Measure the Resistance of the Sensor at the Sensor