JCB Excavator 655 Fault Code: Poor Tractive Effort
Poor Tractive Effort · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault 655 on JCB excavators flags Poor Tractive Effort, meaning the machine is not driving with the power or speed it should. JCB directs technicians to check negative control signals, main pump pressures, track motor relief valve settings, and track motor drain line rates. No numeric thresholds or set-conditions are listed for this code.
Medium severity. Poor tractive effort is a performance complaint rather than an immediate safety shutdown. It should be diagnosed within the shift since it affects the machine's ability to travel, climb grades, or work under load, and ignoring it can hide a developing hydraulic pump, valve, or motor problem.
What does JCB Excavator error code 655 mean?
Fault 655 means the excavator's undercarriage drive system is not delivering the tractive effort (pulling or pushing power at the tracks) that it should. This is a hydraulic performance issue, not a simple electrical short, and it points at the travel circuit: the main hydraulic pumps, the track motors, and the control signals that command them.
JCB's own troubleshooting steps for this code focus entirely on the hydraulic travel circuit. There is no described electrical fault trigger, no specific sensor failure, and no listed numeric threshold. Instead, the code is a symptom flag that tells the technician to go check specific hydraulic and control values on the machine directly.
Because tractive effort depends on pump output pressure, motor relief valve settings, drain line flow, and the negative control signal that governs pump destroking, a weak link in any one of these areas can cause the whole complaint. Diagnosis requires working through each system in turn rather than replacing a single part.
Common causes of 655
- A problem with the negative control signal that regulates main pump output, causing incorrect pump behavior under load.
- Incorrect main pump pressure, which directly reduces the hydraulic power available to drive the tracks.
- Track motor relief valve settings that are out of specification, limiting the torque the track motors can produce.
- Excessive or abnormal track motor drain line flow rates, which can indicate internal motor leakage and lost efficiency.
How to troubleshoot JCB Excavator 655: first checks
- Note what travel gear (speed range) the machine is in when the poor tractive effort occurs, since JCB specifically asks this question as part of diagnosis.
- Test the negative control signal to confirm the main pumps are receiving the correct destroke command.
- Test main pump pressures to confirm the pumps are producing the hydraulic power the travel circuit needs.
- Test the track motor relief valve settings on both track motors to confirm they match specification.
- Test the track motor drain line rates to check for internal motor leakage that would rob tractive effort.
- Check for a related fault 662, since JCB references it alongside 655 as part of the same diagnostic picture.
How the code clears
No reset procedure is listed for this code. It is a symptom-based diagnostic flag, so once the underlying hydraulic cause (pump pressure, relief valve setting, drain line flow, or control signal) is corrected and confirmed by testing, the complaint should resolve without a separate clearing step.
Frequently asked questions
What does JCB fault code 655 mean?
It means the excavator is showing Poor Tractive Effort, that is, the tracks are not producing the drive power expected. JCB ties this to the hydraulic travel circuit rather than to a single sensor fault.
Does travel gear matter when diagnosing fault 655?
Yes. JCB specifically asks what travel gear the machine is in when the problem occurs, since tractive effort and hydraulic behavior can differ between low and high travel range.
What causes poor tractive effort on a JCB excavator?
JCB lists four checks tied to the likely causes: an incorrect negative control signal to the main pumps, wrong main pump pressure, out-of-spec track motor relief valve settings, and excessive track motor drain line flow indicating internal leakage.
Is fault 655 an emergency stop condition?
No. It is a performance complaint, not a listed safety shutdown. However, since it affects travel and pulling power, it should be diagnosed promptly, especially before working on slopes or under load.
Is fault 655 related to any other JCB fault code?
Yes. JCB references fault 662 alongside 655 in the diagnostic notes, so it is worth checking that code as part of the same investigation.
Can I fix fault 655 myself or does it need a dealer?
Basic checks like noting the travel gear and inspecting for obvious hydraulic leaks can be done by an experienced operator or mechanic, but confirming main pump pressures, relief valve settings, and drain line rates typically requires hydraulic test gauges and shop-level diagnostic experience.