New "ECM" (engine computer)

[AKBrick]

Our Motorhome started stuttering (vibration like) when it was about to change gears. It was having problems trying to talk to the Allison transmission to coordinate engine speed/shift change. It turns out that we were getting a "secondary speed pick-up failure" on the diagnostic computer that the tech hooked up. Long story short; first they changed out the speed pick-ups, no go. Then they changed out the speed pick-up wiring harness between the speed pick-ups and the ECM; no go. Finally they changed out the engine computer (ECM) and everything seems to be okay. After 230 miles there were no problems. I'm keeping my fingers crossed from now on until I'm sure that the problem will not come back again. It was definately a stressfull week. This is the first time that we've had to move out of the motorhome for a repair.
Happy trails,
Tom Brickwell

[MrTransistor]

Hi All,

I'll place this here since it's ECM related and might be useful to those with older CAT C7 and 3126 engines.

This was a post I placed on the Winne Owners Forum around 9-7-2006.

Here is information I have obtained on software versions that apply to the CAT C7 350 HP engine as used in newer, Freightliner chassis, Winnebago and Itasca coaches. This is not to imply that this software is for every C7 engine so check with CAT to be sure it is for your serial numbered engine. If you can find someone with a ‘CAT Pocket Tech’ they can read out the data from the ECM to get your engine’s serial number. It may also be that newer software versions are available for the CAT 3126 engines on earlier models that would correct some of these issues.

Our coach left the factory with 2487630 software. It ran great but we had the delay on acceleration problem that seemed to be inherent with the C7. Step on the accelerator and count - one…two…three….etc. - until the power would kick in. This effect is worse at altitude. Sea level is around one second increasing to 4 or 5 seconds at 8000 feet. Annoying at best, dangerous at worst. For some reason, on occasion, this delay would stretch out to 10 to 15 seconds and you’d feel like it was leaving you stranded in an intersection.

We had the ECM re-flashed on Apr. 04 of 2006 under warranty with version 2517445 software in an attempt to correct these issues. No luck! Just had a re-flash done under warranty with version 2725312 software and this time I think they got it right. At our altitude of over 5000 feet, there appears to be no delay at all. Power comes on smoothly from the start and increases as you accelerate. Of course, you don’t get 350 HP at idle and you still get the surge of power at around 2000 RPM as the boost peaks out at 25 inches, but it’s no longer a dead horse pulling away from a light! Drivability is now as it should be.

Don’t know about any other parameters like fuel economy but I’ll know soon since we leave on an estimated 8000 mile trip tomorrow. I’ll report back when I have the numbers.
If you are experiencing these acceleration problems, I would encourage you to contact a CAT dealer and officially complain. This seems to be the way to get warranty work done as opposed to paying $100.00 to ‘just have the ECM re-flashed for no reason‘.

Software
Part # Description
2725312 Production update for emissions margin improvement for VER 3.59.3
2653320 Add low fuel pressure sensor and misc. updates for VER 3.59.1
2595597 Eaton transmission and Misc. updates VER 3.57
2571954 RV acceleration improvement for C7 highway truck VER 3.55.2
2540986 Emissions margin improvement for C7 highway truck VER 3.55.1
2517445 Add application features (MTB shutdown override, J1939 wait to start lamp, plus misc. features) for C7 highway truck, VER 3.55
2487630 Update advance on acceleration (AOA), Eaton autoshift feature and governor gain MAPS (W/4.5 injectors) for ACERT C7 highway truck, VER 3.53.2
2482318 Update cold MAP changes for ACERT C7 highway truck, VER 3.53.1-1
2474613 Update with 4.5 injectors, T-Trim initialization, ECM lockup and coolant temperature trip point for ACERT C7 highway truck, VER 3.53.1
2457558 Update with 4.5 injectors for ACERT C7 highway truck, VER 3.53

*** Each sentence begins with ‘Leased Software (to or for)’ Each sentence ends with ‘PROD, HEP, 10, 2.5 Gram NOX + HC, HEUI-BC, Production Engines’
As in -- 2725312 Leased Software for Production update for emissions margin improvement for VER 3.59.3 PROD, HEP, 10, 2.5 Gram NOX + HC, HEUI-BC, Production Engines ***

Report back on mileage; We now plan trips around 9 plus MPG and see averages of 8.8 to 9.2 or better depending on wind. Bear in mind that we set the cruse on 60 and I accelerate very slowly and coast to most stops.