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329 ECU fuse blows

Gordonmac ยท 2025-05-24 12:44

Hi All, I have a Cat 329 Dl that the ECU blows as soon as the machine isolator is switched on, I disconnected the plug from the ECU mounted on the motor and the fuse did not blow, my suspicion it is the ECU my be damaged. Some background The machine has behaved oddly, the low oil pressure warning would come on and then go away although oil pressure was present, the machine seems to have lost power and then after switching it off and back on the issue would disappear for some time, I wonder if the ECU was not starting to play up. serial no: CAT0329DPTPM00224

Replies8
  1. #1Nige2025-05-24 14:27

    Which ECM are you talking about.? Engine or Machine.? If it is the machine ECM then there are three power wires feeding it. Pins 1 & 13 (both wire 184 RD) are Batt+ and Pin 23 (wire 308 YL) is switched power from the key, both on Connector J2. i would suggest first to check power & ground with the connector unplugged. Ground wires are 235-BK on Pins 2 & 14.

  2. #2Gordonmac2025-05-25 00:42

    Hi Nige Yes, sorry for not clarifying it is the engine ECU 15A fuse that blows, I tested the fuse to ground with the connector unplugged from the engine and did not find continuity to ground on that line Gordon

  3. #3Nige2025-05-25 10:51

    There are three wires that supply the engine ECM with Batt+ and three connected to ground, plus one that is switched power.. Batt+ is 140-RD on Pins 48, 52, & 53 of connector J1. Ground is 229-BK on Pins 61, 63, & 65. Switched power is 308-YL on Pin 70. So there are various pins to check power and ground with the connector unplugged. I would also suggest unpinning all three of the Batt+ wires then re-pin them one at a time to see if you can identify if it is the wire connected to one particular Pin that is blowing the ECM fuse.

  4. #4Nige2025-05-25 11:07

    Another thing to think about. Is there a possibility one or more of those three Batt+ wires could be shorted to ground somewhere between the fuse panel and the engine ECM.?

  5. #5Nige2025-05-25 12:50

    I never thought to ask before. Would an electrical schematic be of any help to you.?

  6. #6Gordonmac2025-05-27 06:24

    Hi Nige That would be of great help, I will be attending to that machine in the next couple of days. Do you have any ecm diagrams ?

  7. #7Nige2025-05-27 09:28

    Check your message inbox.

  8. #8martinderek2026-02-21 08:53

    Good Morning just checking to see what your problem was i have a machine with a very similar issue