JCB Excavator 652 Fault Code: Machine Tracks Off Line During Straight Travel

What does JCB Excavator error code 652 mean?

Fault code 652 describes a symptom rather than a single sensor failure: the excavator does not travel in a straight line when both tracks are commanded to move at the same speed. This usually points to an imbalance somewhere in the hydraulic travel circuit, since each track is driven by its own motor fed from the main hydraulic pump.

Because both tracks share the same pump output but run through separate motors, valves, and relief settings, any difference in flow, pressure, or internal leakage between the two sides will cause one track to turn faster or slower than the other, pulling the machine off line.

This code is diagnosed through a structured test sequence rather than a single fixed trigger value, checking the negative control signal, main pump pressures, relief valve settings, drain line rates, and motor speeds on both sides to find where the imbalance originates.

Common causes of 652

• Negative control signal imbalance between the two track circuits, affecting how much flow each pump section sends to its track motor
• Unequal main pump pressures feeding the left and right track motors
• Track motor relief valve settings that differ from one side to the other, allowing one motor to work against a lower or higher relief limit
• Track motor drain line flow rates that differ side to side, indicating uneven internal leakage or wear in one motor
• Track motor speed differences between the two sides under the same commanded input
• A priority valve in the pump line, on machines fitted with one for a low flow or weedcutter circuit, altering flow balance to the main travel circuit
• Possible cross-connection or swapped hose issues in the main pump service lines

How to troubleshoot JCB Excavator 652: first checks

1. 1Drive the machine in a straight line over a measured 20 meter distance and record how far it deviates, along with the ground conditions at the time, so you have a baseline to compare after each check
2. 2Test the negative control signal to each track pump section to confirm both sides are receiving a matching command
3. 3Check main pump pressures on both track circuits to see if one side is running lower or higher than the other
4. 4Check the relief valve settings on both track motors to confirm they match the specification and each other
5. 5Check the drain line rate from each track motor, a higher than normal drain rate on one side can point to internal wear or damage in that motor
6. 6Compare track motor speeds side to side under the same input signal to isolate whether the fault is in the motor, the valve, or the pump supply
7. 7If the machine has a priority valve in the pump line feeding a low flow or weedcutter circuit, connect the two main service hoses at that valve together and recheck whether the tracking fault changes
8. 8Swap the two main hoses on the hydraulic pump and re-run the straight line test to see if the direction of the deviation changes, which helps confirm whether the fault follows the pump side or the motor side

How the code clears

No separate clearing step is listed for this code. Because 652 describes a physical tracking deviation rather than a stored electronic fault, resolving the issue means correcting the underlying hydraulic imbalance identified during testing (pump pressure, relief valve setting, drain rate, or motor speed) and reconfirming with another straight line test over the same 20 meter distance.