How to diagnose and troubleshoot the Caterpillar 311B Excavator 2LS MID 161 - CID 0168 - FMI 00 fault message?

 This code is generated when the diagnostic circuitry within PL522 and 523 detects a system voltage higher than 32 VDC. Possible causes of this fault include: 

 

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 • A faulty charging system component. 

 • A faulty wiring harness conductor. 

• A faulty PL522 or 523. A module fault is unlikely.

Note: Determine if a battery charger or welding machine is being used on the machine. Disconnect the charger or welding machine from the machine. Recheck for diagnostic codes. 

 Test Procedure 1. Check the system voltage at the 70-pin connector of PL522 or 523.

A. Start the engine and run it at high idle for 5 to 10 minutes. 

 B. Measure the system voltage between the "No Switching Power" and "Ground" contacts. Pin 52 is the "No Switching Power" terminal, and pin 65 is the "Ground" terminal. 

 

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Expected Result: Voltage is 11 VDC to 32 VDC. 

Result: • Normal - Voltage is 11 VDC to 32 VDC. PL522 or 523 should not record this diagnostic code. 

Repair: Clear the diagnostic code from PL522 or 523 using a Caterpillar Electronics Technician (Cat ET). If the voltage is normal and PL522 or 523 records this diagnostic code again, replace PL522 or 523. Before replacing PL522 or 523, please contact your Caterpillar technical communicator.

  Stop • Abnormal - Voltage is not 11 VDC to 32 VDC. Proceed to Test Step 2.

Test Step 2. Check the alternator. 

  A. Run the engine at high idle for 5 to 10 minutes. 

 B. Measure the voltage output at the battery terminals.

  Expected result: The voltage should be below 32 VDC.

 

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 Result: • Normal - Voltage below 32 VDC. The battery may be faulty. Proceed to test step 3.

  • Abnormal - Voltage above 32 VDC. Troubleshoot the alternator. The voltage regulator may be faulty. If no issues are resolved, proceed to test step 3. 

  Test Step 3. Check the battery voltage.

Turn the ignition switch to the off position. Measure the voltage at the battery terminals.  

Expected result: The voltage should be below 32 VDC.

Result: • Normal - Voltage below 32 VDC. Proceed to test step 4. 

    Result: • Yes - Other "CID 168 FMI 00" diagnostic codes can be found on other Electronic Control Modules (ECMs). Repair: Clear the fault if all of the following occur: 

Monitor the module and the machine for any further faults. If the fault recurs, the PL522 or 523 module is not faulty because other electronic control modules are displaying the same fault. Recheck the system voltage. 

Stop • No - No other "CID 168 FMI 00" diagnostic codes can be found on other ECMs. Repair: Clear the fault if all of the following occur: 

 ◦ No fault was found in the charging system. 

 ◦ No fault was found in the wiring.

  ◦ The fault has recurred several times.  

Monitor the module and machine for further faults. If the fault recurs, the PL522 or 523 module may be faulty. The PL522 or 523 should be replaced. Refer to System Operation, Troubleshooting & Repair, Testing & Adjustment, "Electronic Control Module (ECM) - Replacement". After replacing the PL522 or 523, recheck the system and check the status of the diagnostic codes.

  Stop

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How to use the Deutz Diagnostic Tool to diagnose faults?

Using DEUTZ diagnostic tools (based on SerDia software and the DECOM interface) to diagnose faults requires following a standardized process: safety preparation → hardware connection → software communication → fault code and data parsing → action testing and calibration → repair verification → report archiving. The core is to differentiate between current and historical faults, combine freeze frames and data streams to pinpoint the root cause, and avoid blindly replacing parts based solely on fault codes.

 

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 1. Establishing a connection: Common locations for the diagnostic port: right side panel of the cab, under/behind the seat, near the ECU next to the engine, inside the fuse box; in construction machinery (such as road rollers), it is often located in the footwell or side panel. Interface type: OBD-II (highway vehicles) or DEUTZ dedicated 3-pin/6-pin CAN interface (non-highway equipment).

  2. Connection Steps: With the engine off, connect the adapter to the vehicle's diagnostic port;

      Connect the adapter's USB end to the computer and open the SerDia software;

      Turn the key to the ON position (without starting the engine) to power on the ECU.

  3. Establish Communication Select "Diagnostics → Connect ECU" in the software, automatically scan or manually select the protocol (CAN/K-Line); Select the corresponding engine model and ECU (e.g., EMR4 EDC17), and wait for the "Communication Successful" message; If it fails: Check the adapter driver, diagnostic port power/ground, and CAN line termination resistance (approximately 60Ω).   

4. Core Diagnostic Process (Key to Fault Location)

 Step 1): Read and Classify Fault Codes (DTCs) Enter "Fault Code Management" and read the current fault (Active), historical faults (History), and pending faults (Pending); 

      2). Record complete information: DTC code (e.g., P0340, SPN+FMI), fault description, number of occurrences, freeze frame (speed, load, temperature, voltage, etc. at the time of the fault);

   3), priority principle: handle the current fault first, then analyze historical faults; communication faults (starting with U) take precedence over sensor/actuator faults.  

Step 2: Freeze Frame and Data Stream Analysis (Reconstructing Fault Conditions) 

 

 

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5. Freeze Frame and Data Stream Analysis (Reconstructing Fault Conditions)  

 1) Retrieve freeze frames to confirm the boundary conditions at which the fault occurred (e.g., idle/full load, cold/hot engine, regeneration stage). 

2) Enter "Real-time Data" and add key parameter groups for monitoring: 

a) Power System: Battery voltage, ECU power supply voltage; 

 b) Intake System: Intake pressure (MAP), intake temperature, boost pressure; 

 c) Fuel System: Common rail pressure (actual/target), metering valve opening, injector drive status;

 d) Timing System: Crankshaft/camshaft speed, phase deviation; 

 e) Aftertreatment: NOx sensor, DPF differential pressure, regeneration status; 

3) Anomaly Judgment: Compare with standard values ​​(e.g., idle common rail pressure approximately 500–800 bar) and observe whether the parameters change synchronously with the operating conditions (e.g., whether the accelerator pedal opening and fuel injection quantity are linear). 

 4. Operational Testing and Circuit Verification (Distinguishing Component/Wire/ECU Faults)   

  1) Check "ECU Information": Software version, hardware serial number, calibration number, and confirm if it is the latest version; 

 2) Verify key calibrations (such as injector correction codes, idle speed, regeneration strategy). If they do not match the vehicle model, recalibration is required (original manufacturer authorization required).

6. Repair Verification and Fault Code Clearing 

 1) Repair Implementation: Based on the location results, repair the wiring, replace faulty sensors/actuators, clean or replace filters, update ECU software, etc.;

 2) Clear Fault Codes: After repair, go to "Fault Code Management" → "Clear Fault Codes" to confirm that all DTCs have been cleared; 

  

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IMPORTANT! Handle empty accumulator tanks in compliance with local regulations.

 

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Relieving the pressure

1   Close the return valve. Unscrew the pressure limiting valve.

 

 

 

2   Connect the return hose from the filling

equipment return connection to the union marked Y/Z or L3/L4 on the accumulator as illustrated.

 

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3   Open the return valve on the filling

equipment. The oil will now be returned to the filling equipment tank.

4   Oil can be drained from the pipe using

compressed air. The connections on the

master cylinder and centering cylinder must then be undone.

5   Remove the protective cap on the gas side of the accumulator tank.

6   Undo the plug on the gas side max 2 turns and allow the gas to seep out.

7   Remove the plug completely

 

 

1 Protective cap

2 Plug