Compressor Airend Oil Pressure Below Safe Threshold
The ATLAS-COPCO-E004 (Atlas Copco Xc4002 / Xc2003 / Xc4004) diesel fault code means: Compressor Airend Oil Pressure Below Safe Threshold. This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- moderate
- Estimated cost
- DIY oil and filter service $30-$80 in parts. Sensor replacement $50-$150 parts plus 1-2 hours labor. Oil pump replacement or airend overhaul $800-$3,500+ at a service center depending on damage.
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Common Symptoms
- Controller LCD on the side panel displays E004 and machine shuts down immediately
- Red fault light is solid on the Xc4002 / Xc2003 / Xc4004 panel
- Compressor loads briefly then trips off within seconds of reaching pressure
- Machine will not return to RUN state after reset attempt without clearing the fault root cause
- Oil pressure warning lamp illuminates just before or at shutdown
- Air delivery to the hose drops to zero as the unit unloads and stops
- Audible alarm sounds continuously at shutdown before the engine cuts out
Probable Causes (Ranked by Likelihood)
- Low compressor oil level in the airend sump, oil consumed or not topped off before use Very Likely
- Faulty or stuck oil pressure sensor sending a false low-pressure signal to the controller Likely
- Clogged compressor oil filter restricting flow through the lubrication circuit Likely
- Failed or worn compressor oil pump not building adequate pressure at operating RPM Possible
- Internal airend bearing wear or seal failure causing pressure bleed-off in the oil circuit Possible
- Wrong viscosity oil used in the airend, causing insufficient film pressure especially in cold weather Less Likely
- Wiring fault or broken connector between the oil pressure sensor and the Xc4002 / Xc2003 / Xc4004 controller Less Likely
Step-by-Step Diagnostic Procedure
Start with the basics. With the machine shut off and cooled down, pull the airend oil dipstick or sight glass and check the oil level. It must be in the safe operating band marked on the unit. Low oil is the most common cause of E004. Top off with Atlas Copco-specified airend oil only, not engine oil.
Check the oil condition while you are in there. If the oil looks milky, foamy, or very dark with particles, it is contaminated or overdue for a change. Do not restart until the oil is changed and the cause of contamination is found.
Inspect the compressor oil filter. On most XAS series towables the filter is accessible on the side of the airend frame. If the filter has not been changed at the service interval (typically every 500 hours or annually), replace it now. A bypassed or clogged filter will starve the circuit.
Reset the fault on the Xc4002 / Xc2003 / Xc4004 controller by pressing STOP, waiting 10 seconds, and cycling back to AUTO or RUN. Watch the oil pressure reading on the controller LCD in the first 10 seconds of operation. Normal compressor oil pressure on most XAS platforms is 2.0 to 4.0 bar (29 to 58 psi) at operating RPM. If pressure does not rise into range, shut down immediately.
Check the oil pressure sensor and its wiring. The sensor is typically a single-wire or two-wire sender mounted on the airend oil manifold. Inspect the connector for corrosion, pushed-back pins, or chafed insulation. Use a multimeter set to DC voltage or resistance to verify the sensor output matches specs in the service manual. A sensor that reads zero at idle even with good oil level is likely failed.
If you have DiagPro service software via the J1939 / CAN data port, connect and read the live oil pressure value reported by the controller. Compare it to a mechanical gauge installed at the same port if possible. A large discrepancy between the live sensor value and the mechanical gauge confirms a failed sensor or wiring fault rather than an actual lubrication problem.
If oil level, filter, sensor, and wiring all check out and the machine still trips E004 with low or no oil pressure confirmed by a mechanical gauge, the oil pump or internal airend condition is suspect. This requires disassembly and is an advanced repair. Stop operation and contact an Atlas Copco service technician before further damage occurs to the airend.
Frequently Asked Questions
What does Atlas Copco code E004 mean?
E004 means the Xc4002 / Xc2003 / Xc4004 controller detected that oil pressure inside the compressor airend dropped below the minimum safe level. The controller shuts the machine down immediately to prevent the airend from running dry and seizing. It is one of the most serious faults the machine can throw.
Can I keep running the compressor with E004 active?
No. The machine will not stay in RUN with E004 active. Even if you could bypass it, running an airend without adequate oil pressure for even a few minutes can cause permanent bearing damage and total airend failure, which is a multi-thousand-dollar repair. Do not attempt to bypass or override this shutdown.
How much does it cost to fix E004?
If the cause is just low oil or a dirty filter, you are looking at $30 to $80 in parts and you can do it yourself in under an hour. A bad pressure sensor runs $50 to $150 plus labor. If the oil pump has failed or the airend has internal damage, expect $800 to $3,500 or more at a service center depending on how long it ran without pressure.
My oil level looks fine. Why am I still getting E004?
A full sight glass rules out the most common cause but does not clear the fault automatically. The next most likely culprits are a failed oil pressure sensor giving a false reading, a clogged oil filter starving the pump, or a wiring fault between the sensor and the controller. Use DiagPro service software via the J1939 / CAN data port or a mechanical gauge to confirm whether actual pressure is low or the sensor is lying to the controller.