This article describes how to solve the caterpillar 311b excavator 2ls MID 122 – CID 1251 – FMI 03 fault
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Conditions that generate this code: The Product Link module tracks machine hours and reports them to the office. The alternator R-terminal signal is used to detect when the machine is operating. If the input continuously receives a voltage signal above the normal range, the machine operation will not be detected. If the input continuously receives a voltage signal above the normal value, the reported service meter hours (SMU) will be inaccurate.
Test Step 1. Check the R-terminal cable for a short to the battery.
A. Disconnect the Product Link cable (P1) from the Product Link module.
B. Measure the resistance from the alternator R-terminal input J1-4 (403MC9-GN-18 to the battery (J1-1).
Expected Results: Resistance should be greater than 5000 ohms.
Result:
• OK – The Product Link harness appears to be normal. Go to Test Step 2.
• NO – The Product Link cable may be shorted to the battery. Repair: Repair the cable and verify that the fault is eliminated.
STOP TEST STEP 2. CHECK PRODUCT LINK HARNESS FOR SHORT TO VOLTAGE SOURCE.
Expected Result: No stable DC voltage equivalent to the battery voltage is measured when measuring the AC generator R-terminal input. Result:
• OK – The signal is a 0 kHz to 2 KHz 11 VDC to 32 VDC square wave or a steady DC voltage equivalent to the battery. The Product Link harness may not be faulty. Go to Test Step 3.
• Not OK – The Product Link cable may be shorted to a DC voltage other than the battery voltage. Repair: Repair the cable and verify that the fault is eliminated. Stop
Test Step 3. Check the Machine Alternator.
A. Disconnect the Product Link machine cable from the alternator.
B. Start the engine.
C. Measure the alternator R terminal to verify that a 0 kHz to 2 KHz 11 VDC to 32 VDC square wave is present. A steady DC voltage equivalent to the battery voltage should not be present.
Expected Results: You should have a 11 VDC to 32 VDC square wave at the alternator R-terminals at 0 kHz to 2 KHz.
Result:
• OK – There is a 11 VDC to 32 VDC square wave at 0 kHz to 2 KHz at the alternator R-terminals. Go to Test Step 4
. • Not OK – There is no 11 VDC to 32 VDC square wave at 0 kHz to 2 KHz at the alternator R-terminals. Repair: Repair or replace the alternator. Stop
Test Step 4. Check if the diagnostic code is still active.
A. Clean all contacts on the harness connectors.
B. Reconnect all harness connectors.
C. Turn the key start switch to the ON position and operate the machine.
D. Use Caterpillar Electronic Technician (Cat ET) to determine if the “CID 1251 FMI 03” diagnostic code is present.
Expected Result:
The “CID 1251 FMI 03” diagnostic code is present. Result:
• Yes – This fault has not been corrected. It is unlikely that the ECM is faulty.
Repair:
Repeat this diagnostic test procedure. If the cause of the diagnostic code is not found, replace the Product Link ECM. Contact your Caterpillar Technical Communicator before replacing the Product Link. Refer to Systems Operation, Troubleshooting, Testing and Adjusting, “Electronic Control Module (ECM) – Replace”. STOP
• No – No diagnostic code exists. This fault does not exist at this time. The initial problem may have been caused by a poor electrical connection or short when disconnecting and reconnecting one of the harness connectors. Return the machine to normal operation. STOP
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