I have a 29’ Extreme with a 525. Engine was rebuilt several years ago and punched out to 540cid. Whipple flashed ECM. Lately, engine goes into Guardian mode at around 4800rpm. Smart craft and computer shows overspeed fault. We are thinking maybe bad ECM or problem in harness. Any other ideas would be appreciated. Thanks!

I’d check grounds/connections first. Had this issue other my forward engine and the ring terminal connection was bad. Looked like it was plugged in but bad. As Caterpillar calls it… the wiggle test. Mine wouldn’t pull past 4400 rpm. 525s w/ whipple ECMs

All connections good. Replaced water pressure and throttle position sensors based on fault codes and computer diagnostic messages post guardian mode. Problem still persists. I have a flashed ECM. Could that have gone bad? Wiring harness problem? Driving us nuts! Any more suggestions would be greatly appreciated. Thanks in advance

Any new fault codes after the reset ? are you running a whipple SC or they just remapped it

Same fault codes. Engine still goes into Guardian at 4800rpm. The engine was punched to 540 cid several years ago. Not a whipple SC. Just remapped to 5800. It’s crapped three map sensors over the years, otherwise no problems.

are you getting beeps ? and how many and intervals

https://www.perfprotech.com/blog/mar...ng-horn-alarms