pcmhacking.net

Wondering if anyone can shed some light on an issue I'm having.
Swapped out a vs na v6 engine i set up some years ago in a ski boat with a vx l67. I had a custom tune done by my local performance centre with no vats, pcm, oxygen sensors, bcm etc. The engine will start and run but doesn't develop the power it should, hunts at idle and periodically takes a lot of winding over to start. But the biggest issue is that we can't connect to the ecu. An oscilloscope shows voltage at both data pins on the diagnostic plug but only one registers signals. Could this be a shot ecu or can the custom tune be messing it up (can't see how).
I am wondering if the quickest solution might be a haltech ecu to guarantee coms and also let me easily alter idle etc. My worry is that without oxygen sensors and an ability to dyno then tuning is near impossible unless i can get a haltech tune for this engine from somewhere. Not after gobs of power, a standard tune would be plenty, just want a bit more go than the na engine and good reliability.
Any suggestions greatly appreciated.

are you using VS ECU with MAF meter?

If so just use enhanced mod and tune it yourself or get them to alter it, shouldn't take much, just remove vats, set it a manual box, you might just need to play around with stop screw to help if you have no speed sensor on it.

There is only 1 data pin outputting 8192 baud aldl at the diagnostic plug pin 9 see pic below.does it still have the vs ecotec loom and ecu with a vs l67 tune on the memcal or has someone stupidly fitted a vx l67 tune into it or has it all be swapped to vx wiring.know what loom and ecu is in there it should be easy to just start fresh like suggested above and turn off vats set to manual and burn to a meal to get it going deceint.

The loom and ecu were both replaced with vx ones. It runs MAF sensor, just no oxygen sensors as water is dropped into the exhausts to keep them cool. The data plug is wired as shown so I'm not sure why we can't connect to ecu.

Sorry I missed the fact that ECU and loom were changed.

It sounds like its not running at all and its in limp home mode. You should be able to key on and read data if you cable is ok, if not either the wiring to the data plug is shot or the pcm is not running at all (hardware or software wrong/broken). A haltech wont make your life easier, the type of computer isnt the problem here.

Thanks for your help. I will try and get another vx pcm and try that. The wiring to the obd plug is definitely ok and i don't think its software as i have tried to connect with the factory memcal and no joy there either.

What kinda cable and software and files are you trying to connect with tunerpro etc

I took the boat to the performance centre that originally tuned our na vs motor. He did the tune for the l67 but was unable to connect to the ecu. He also checked the obd plug wiring and found it ok. Not sure of the exact setup, but he was using a snapon scan tool and even tried his older model with no success. He is a reputable performance tuner, unfortunately without much time for my project!
I don't think it is running in limp mode, it runs well between 2000rpm and 4000rpm, but doesn't pull away as good as the na did and will only run out about 5kmh faster at full throttle (4500rpm is as hard as it will push the boat).
Before the engine was removed from the car it had heaps of go. It didn't idle great but I put this down to the vacuum lines being connected incorrectly. Since installing it in the boat however, no-one can connect to the ecu, wish i tried before I removed it!
I am certain the OBD wiring is correct, I have checked and rechecked the pins, continuity tested the wires and the oscilloscope is registering both voltage and signal, but 3 different scan tools won't connect and all of them have never had trouble connecting to these model vehicles.
Is it possible that the tune could prevent connection? If so then putting the original memcal back into it should let us connect shouldn't it? (it doesn't)
Im thinking it has to be ecu, but it seemed ok in the car.

Yeah it sounds like it. Maybe a wiring fault at some stage blew out the aldl chip. Maybe the tune is something aftermarket. Probably best to ask for details and maybe a working setup from the original tuner. But having said that all tools and adx files might be looking for the bcm too. Can the delco flash tool detect the the pcm when configured for bench pcm use? what files are you using to connect?