Missfire on first start

[V8CHRGD]

Hi Everyone,

This morning on first start up my VF 6.0 L77 started with a misfire and had a message saying service ESP. It lasted about 10 seconds then idled as normal and i turned it off as i just needed to move the car. Started it up again a couple hours later and it started fine with no misfire or warning on the dash but took it down to Supercheap auto and got them to do a ecu scan. An error came up as U0401 under the heading 8.1 and i have attached a picture of the error. Reading through the threads on this site i see people having similar problems with LS3 engines requiring the injectors to be replaced but haven't found much info on this problem with L77 engines. Mine has only had the misfire with error message once and drives smooth as per normal so im wondering if i should replace spark plugs and leads and hope for the best as the car has only done 56K. Not keen on taking it to a Holden dealer (had issues with there work on a previous car) but if any one knows a mechanic/shop in Perth that is knowledgeable with the GM v8's please comment.
Thanks for taking the time to read, appreciate any advice/ comments/ personal experience etc.

Cheers.

 

[Skylarking]

U codes are associated with communication issues.

P codes are associated with power train issues.

An injector fault will result in a P code such as (from memory) P0300 which is multiple cylinder misfire or P0302 which is cylinder 2 misfire. The known LS3 injector issue will result in such cylinder misfire codes so doubt this is your problem.

If many modules report such U codes, it could be a battery voltage related issue so doing a battery load test will identify if the cause is indeed the battery, otherwise the alternator may not be charging the battery correctly and voltage drops when starting.

If it’s only the ECU reporting a U code, it could be a wiring issue or corrosion on the connector pins. Disconnecting the ECU plug and examining the pins in detail for mechanical issues and then spraying contact cleaner on the wiring and ECU sides of the connectors/plug before reconnecting may solve the issue...

I may be completely wrong but it’s a simple thing to try...

 

[V8CHRGD]

If it happens again i will try this method, cheers.