MSS3s Machine Security System Caterpillar


Engine Does Not Start and Status Indicator Is Continuously Red

Usage:

120G 11W
A solid Red LED in the status indicator indicates that the MSS has not recognized a valid electronic key for that machine. This condition can be caused by several problems. One or more of the problems that are listed here could be responsible for this condition. If the electronic key has been damaged, the MSS will not disarm and the machine will not start. If a problem exists in the exciter coil, the MSS will be unable to read the electronic key. If the wiring for the exciter coil is damaged, the MSS will be unable to read the electronic key.

Note: Ensure that you have only one electronic key near the exciter coil when the MSS reads the key. Do not have more than one electronic key is near the exciter coil. If multiple electronic keys are present, the MSS3s ECM will not be able to read the key and the machine will not start.

Table 1
Troubleshooting Test Steps  Values  Results 
1. CHECK THE KEY.

A. Connect the Cat Electronic Technician (Cat ET) to the Service Connector.

B. Insert a valid electronic key for the machine in the key start switch.

C. Turn the key switch to the ON position.

D. Go to the "Service/Security Management" screen. Check the "Current Key Information".

E. Check the "ID1" and "ID2" for the key that is in the key start switch. 

The MSS reads the ID1 code and the ID2 code as 0. 
Yes - The MSS reads the ID1 code and the ID2 code as 0. The key may have failed or the problem may exist in the exciter coil.

Proceed to Test Step 2.

No - The MSS reads the ID1 code and the ID2 code correctly. The key has been read by the MSS3s ECM, but the MSS is still armed. The MSS still armed, indicates that the key in the key start switch is not authorized for that machine.

Repair: Program that key into the MSS3s ECM or use a different key.

STOP.

 
2. CHECK THE EXCITER COIL.

A. Disconnect the exciter coil from the wiring harness.

B. Measure the resistance on the leads of the exciter coil. 

The resistance is approximately 1 ohm. 
Yes - The resistance is approximately 1 ohm.

Proceed to Test Step 3.

No - The resistance is greater than approximately 1 ohm. The exciter coil has failed.

Repair: Replace the exciter coil.

STOP. 
3. CHECK THE WIRING OF THE MACHINE HARNESS FOR AN OPEN CIRCUIT.

A. The exciter coil remains disconnected from the wiring harness.

B. On the harness side of the connector for the exciter coil, install a jumper wire between pin 1 and pin 2 .

C. Disconnect the wiring harness connector from the MSS3s ECM.

D. Measure the resistance between pin 7 and pin 53 of the connector for the MSS3s ECM. 

The resistance is less than 5 ohms. 
Yes - The resistance is less than 5 ohms between pin 7 and pin 53. The wiring for the exciter coil is correct

Proceed to Test Step 4.

No - The resistance is greater than 5 ohms between pin 11 and pin 13. There is a problem in the wiring for the exciter coil.

Repair: Check the wiring harness for signs of damage. Repair or replace the machine harness.
Note: The "ferrite coil" assembly is wired in series with the harness of the exciter coil. Locate the "ferrite coil" assembly. The "ferrite coil" assembly is located near the 70-pin connector of the MSS3s ECM. Continuity should exist through the coil assembly.

STOP. 
4. CHECK THE WIRING OF THE MACHINE HARNESS FOR A SHORT TO GROUND.
Note: The output drivers of the MSS3s ECM are protected from excessive electrical current. Excessive electrical current is usually the result of a wire or a component that is shorted to ground. If the MSS3s ECM detects an excessive amount of electrical current, the MSS3s ECM will disable the output driver.

A. The wiring harness connector for the MSS3s ECM and the exciter coil remain disconnected.

B. The jumper wire remains installed.

C. Measure the resistance between pin 7 of the MSS3s ECM and frame ground.

D. Measure the resistance between pin 53 of the MSS3s ECM and frame ground. 

The resistance is greater than 5000 ohms. 
Yes - The resistance is greater than 5000 ohms. The resistance is correct.

Proceed to Test Step 5.

No - The resistance is less than 5 ohms. The wiring harness is shorted to ground.

Repair: Check the wiring harness for signs of damage. Repair or replace the machine harness.

STOP. 
5. CHECK THE WIRING OF THE MACHINE HARNESS FOR A SHORT TO + BATTERY.

A. The wiring harness connector for the MSS3s ECM and the exciter coil remain disconnected.

B. The jumper wire remains installed.

C. Measure the resistance between pin 7 and pin 24 of the connector for the MSS3s ECM.

D. Measure the resistance between pin 53 and pin 24 of the connector for the MSS3s ECM. 

The resistance is greater than 5000 ohms. 
Yes - The resistance is greater than 5000 ohms. The resistance is correct.

Repair: The ECM has failed. The ECM is unlikely to have failed. Perform the previous Test Steps again. If the cause of the problem is not found, replace the ECM. See Troubleshooting, "ECM - Replace".

STOP.

No - The resistance is less than 5 ohms. The wiring harness is shorted to the + battery circuit.

Repair: Check the wiring harness for signs of damage. Repair or replace the machine harness.

STOP. 

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