The 3406E ECM failures we see most

The 3406E has been on the road since 1994 and its ECMs fail in predictable ways. Almost all of it is repairable.

Dead cylinder or misfire that follows the ECM

What you see: A dead hole, a cylinder cutout test that shows one injector doing nothing, or a derate that stays after you swapped the injector.

What's happening: The injector driver stage inside the ECM has failed. On 3406E modules this is the single most common fault.

What we do: We rebuild the driver circuit and bench-fire every injector channel before it ships back.

No communication with Cat ET

What you see: The engine may run, but ET (or any J1939/ATA tool) will not connect. You cannot read codes or program it.

What's happening: The data-link side of the module has failed while the engine-control side still works, or the module is dead entirely.

What we do: We restore the data link on the bench so the ECM can be read and programmed again.

No power-up, no start, no codes

What you see: Key on, nothing. No ECM power, no injector pulse, sometimes intermittent after heat or vibration.

What's happening: Internal power supply or ground-path failure, often corrosion or a cracked joint on the connector side of the board.

What we do: We repair the supply and connector-side faults at the component level and load-test the module.

Sensor codes that make no sense

What you see: A string of 5-volt sensor codes at once (throttle, boost, oil pressure) that survives sensor swaps.

What's happening: The regulated 5-volt sensor supply inside the ECM is shorted or sagging.

What we do: We repair the sensor supply regulator and verify every sensor channel on the bench.

Don't see your exact symptom? Send it in anyway. We bench-test every unit before we tell you what's going on, and if we fix it the diagnostic cost you nothing.

3406E arrangements and ECMs we repair

Give us your engine serial prefix and we know which module you have.

ArrangementECM generation / connectorOur bench
2WSADEM III, 70-pin (157-3705)2 days
1LW, 6TS, 5DSADEM II, 40-pin (117-4017, 145-7806)about a week
5EK (1994-95)ADEM II, 40-pinabout a week
4CK, 8TC (3406B/C)PEEC, pre-ADEM (9X8085)about a week

How the repair goes

  1. 1

    Ship it in

    Self-ship free, or add a prepaid UPS label. Drop-offs in Princeton, MN by appointment. Include your engine serial number.

  2. 2

    We test it

    $350 bench fee, credited toward the repair. We tell you exactly what failed, usually within a day of receipt.

  3. 3

    We fix it

    Injector driver repair, communication restoration, power-supply and 5-volt sensor supply repair, parameter recovery, whatever it needs. 2 days on the bench.

  4. 4

    Back to you

    Programmed to your engine, every channel bench-tested, 2-year warranty. Status email at receipt, at diagnosis, and at ship.

3406E exchange units we stock

If yours is beyond repair, or the truck can't wait: remanufactured, bench-tested, programmed to your engine serial, 2-year warranty. Usually ships the same day.

Questions we get on 3406E ECMs

How much does a Cat 3406E ECM repair cost?

$745 flat, bench fee included. The $350 bench-test fee you pay at checkout credits 100% toward the repair, so the diagnostic costs nothing if we fix it. If it is not repairable we tell you first and offer a tested exchange unit with the bench fee credited.

How long does a 3406E ECM repair take?

The 70-pin 2WS module is 2 days on the bench, plus 1-3 days return shipping. 40-pin 1LW, 6TS and 5EK modules and the PEEC 4CK/8TC run about a week.

Will it come back programmed to my engine?

Yes. Send your engine serial number with the unit and it ships back programmed and bench-tested, ready to plug in.

Can you repair a 3406E ECM the dealer condemned?

Usually. A dealer "no communication" or "failed" verdict is where most of our 3406E work starts. Send it in; the bench fee credits to the repair.

Related: Cat 70-pin ECM problems & symptoms · C15 ECM repair · C12 ECM repair · C10 ECM repair

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What truck owners & shops say

★★★★★
"Mike does great work and sent my repaired ECM back to me right away. Saved me thousands of dollars vs. using the dealer. Would recommend to anyone that needs prompt repair."
Michael B. via Google
★★★★★
"From ECMs and harnesses to straight-out cutting counter bores in-frame for us. Great shop — and a great person to have in your pocket."
Mega24v via Google
★★★★★
"Highly recommend these guys! Fast turnaround — I had my ECM back and repaired by the next day. Will definitely do more business in the near future."
Javon Z. via Google
★★★★★
"Michael is a diesel guru. He made my rig scream and had it done when he said, for the price we agreed to. I'd highly recommend him."
Glenn S. via Google
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"Mike is highly knowledgeable in all areas of diesel repair — from mechanical work to advanced electrical diagnostics. You can count on him to get the job done right."
David F. via Google
★★★★★
"Mike is a very professional and skilled mechanic. I highly recommend him for any of your needs."
Justin N. via Google

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