EPROM Write Failure: Non-Volatile Memory Save Error
The CARRIER-TRANSICOLD-00246 (APX Microprocessor Control System) diesel fault code means: EPROM Write Failure: Non-Volatile Memory Save Error. This is a critical severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- DIY reset and electrical inspection: $0-$50 in supplies (contact cleaner, connectors). Controller board replacement (parts + labor): $800-$2,500 depending on unit model and labor rates. Battery replacement if the root cause: $150-$350 installed.
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Common Symptoms
- Alarm code 00246 appears on the Display Module LCD
- Unit may shut down or refuse to restart after a power cycle
- Configuration settings, setpoints, or alarm history appear reset to defaults after a shutdown
- Unit logs the fault repeatedly even after clearing it with the MENU key
- Display Module shows controller in a fault state at startup
- Unit runs erratically or loses previously saved operating parameters
- Alarm buzzer sounds and the unit stops refrigerating
Probable Causes (Ranked by Likelihood)
- Corrupted or failed EPROM/flash memory chip inside the APX controller board due to age, heat, or voltage spike Very Likely
- Voltage spike or power surge during a write operation that corrupted the non-volatile memory contents Very Likely
- Low or unstable DC supply voltage to the controller causing an incomplete write cycle Likely
- Loose or corroded wiring harness connector at the controller board causing intermittent power loss during a memory save Likely
- Controller board moisture intrusion or corrosion on the EPROM memory circuit traces Possible
- Software or firmware glitch requiring a full controller reset to clear a one-time write error Possible
- Failed or failing APX controller board requiring full replacement Less Likely
Step-by-Step Diagnostic Procedure
Step 1 -- Clear the alarm first. Use the MENU key on the Display Module to scroll to the alarm log, select alarm 00246, and clear it. Cycle the unit to OFF and back to AUTO. If the code does not return, treat it as a one-time event and monitor closely.
Step 2 -- Check DC supply voltage to the controller. With the unit running, measure the DC voltage at the controller board power input connector. You should see 12 VDC (plus or minus 0.5 V) on a 12-volt system or 24 VDC (plus or minus 1 V) on a 24-volt system. Voltage outside this range during a write cycle can corrupt EPROM data.
Step 3 -- Inspect the battery. A weak or failing battery can cause voltage dips during compressor or engine load changes. Check battery voltage under load. Below 11.8 VDC on a 12-volt system or 23.5 VDC on a 24-volt system under load indicates a battery that needs replacement.
Step 4 -- Inspect wiring and connectors at the APX controller. Look for corroded, loose, or backed-out pins in the main harness connector at the controller board. Clean corroded pins with electrical contact cleaner and reseat all connectors firmly. A loose ground connection is a common cause of intermittent voltage drops during memory writes.
Step 5 -- Check for moisture inside the controller housing. Open the controller enclosure and look for signs of water intrusion, condensation tracks, or corrosion on the board surface, especially near the EPROM or flash memory area. Dry the board and treat corrosion with electrical contact cleaner if accessible. Note: internal board repair requires a qualified technician.
Step 6 -- Perform a full controller reset. Some APX units support a factory parameter reset through the Display Module service menu. Consult your unit's service manual for the correct key sequence. This can resolve a corrupted configuration table without replacing hardware.
Step 7 -- If the code returns immediately after clearing, or returns within the first few operating hours repeatedly, the APX controller board itself has likely failed internally. At this point the repair requires a controller replacement by a qualified Carrier Transicold technician. Do not continue operating the unit unmonitored with a repeating 00246 alarm, as setpoint and alarm configuration data cannot be reliably saved.
Frequently Asked Questions
What does Carrier Transicold alarm code 00246 mean?
Code 00246 means the APX microprocessor controller tried to write or save data to its internal non-volatile memory (EPROM or flash) and the operation failed. This matters because the controller stores your setpoints, alarm configuration, and operating parameters in that memory. If it cannot write reliably, the unit may lose its settings after a power cycle or behave unpredictably.
Can the unit still refrigerate with code 00246 active?
Sometimes, yes, for a short period, but you should not rely on it. The unit may continue running on its last saved settings, but if it loses power or shuts down, it may come back up with default or corrupted settings. That means your temperature setpoints could be wrong after a restart, which is a serious problem for a loaded reefer trailer. Treat this as an urgent fault.
How much does it cost to fix alarm 00246?
If clearing the alarm and tightening electrical connections solves it, your cost is minimal, maybe $0-$50 in supplies. If the root cause is a bad battery, expect $150-$350 installed. If the APX controller board has failed internally and needs replacement, budget $800-$2,500 depending on the Vector or Supra model and local labor rates.
Will clearing the alarm code fix the problem?
Clearing it once and watching for a return is the right first step. A single occurrence can be caused by a momentary voltage dip or power surge during a write cycle. If the code comes back within a few hours of operation or returns immediately at the next startup, the controller board itself is likely failing and needs replacement by a qualified technician.
Sources
This page is built from documented references. Verify against your own service info before repair work.