Engine light on, but no error code!

[Wesleyrpg]

hey guys.....its been a while,

got an interesting problem, you see 95% of the time my engine light is on, but when i go into diagnostic mode the engine brings up code 12 (no fault found)

i've noticed a little difference in performance, and my fuel consumption is out of control! Could it be in limp home mode?

the light used to come on when your gave her a bit....ie took her over 3k, but now the light is on pretty much all the time. Occasionally it will misfire for one second when its changing from engine light on, to engine light off.

I thought it might of been the oxy sensor....replaced it and made no difference.....any thoughts?

[88GreenVN]

hey guys.....its been a while,

got an interesting problem, you see 95% of the time my engine light is on, but when i go into diagnostic mode the engine brings up code 12 (no fault found)

i've noticed a little difference in performance, and my fuel consumption is out of control! Could it be in limp home mode?

the light used to come on when your gave her a bit....ie took her over 3k, but now the light is on pretty much all the time. Occasionally it will misfire for one second when its changing from engine light on, to engine light off.

I thought it might of been the oxy sensor....replaced it and made no difference.....any thoughts?

The fault normally has to exist of a while for it to register a code - like if the car is running lean for more that 30 seconds it will register a code.

Have you tested the temp sensor? A drinking problem if not the o2 sensor can be the temp sensor gone bung. Also you should check to see that the o2 sensor is connecting OK. When I did my o2 the plug was not making good contact and yep the car had consumption issues big time.

[vn calais manual]

youd know if it were in limp mode, try changing your water temp sensor. and see how u go.

[Wesleyrpg]

ok i replaced the water temp sensor today, reset the ECU and still the engine light is on! (what a nightmare of a job on the s1 motor)

diagnostic mode still shows up error 12.

can the car be satefy started while in diagnostic mode or am i only meant to read the codes with the ignition on?

[iRiot]

could be the crank angle sensor i had the happen a few times

[greenacc]

maybe the air flow sensor connection.... wobble the connectors to all the sensors you can find. one might be loose.

[vnv8driver]

Ive had this problem with a few customer cars, most of the time its the ecu itself.

Ive had one case where it happened for a while and the car stopped workign completely, and still a code 12 was showing up when in diag mode.


So try a 2nd hand ecu/memcal and go from there.

[Wesleyrpg]

found the problem today...YAY....finally it's fixed!

replaced the ECU....helped for 5 mins.....then the dreaded light came back.

replaced the coil pack and dreaded series 1 DFI module, with a VT one......everything is now ok.....working beautifly!

in fact i think i have more power now than ever before....loves to light up the rear tires in first gear!

[neobristol]

how do i check error codes on a v6? my management light came on for about 15 seconds the other day, i wonder if ive upset something as i replaced both knock sensors on saturday trying to cure another problem. Oh the car seems to misfire on idle when the engine is upto operating temp, and it seems to have abit of vibration when cruzing around 80k's, any idea's? this problem only happens on petrol on lpg it runs fine.

[88GreenVN]

how do i check error codes on a v6? my management light came on for about 15 seconds the other day, i wonder if ive upset something as i replaced both knock sensors on saturday trying to cure another problem. Oh the car seems to misfire on idle when the engine is upto operating temp, and it seems to have abit of vibration when cruzing around 80k's, any idea's? this problem only happens on petrol on lpg it runs fine.

Do you have 2 knock sensors? - or are they O2 sensors in the exhaust?

V6 rough idle when hot can be many things - DFI, Coils/leads/plugs or CAS

[neobristol]

yeah i have 2 i just realised im in the vn section, i should be in the vx!, I have new coils plugs and leads.

[Brin]

How would you know if you were in "limp home mode.."?

My engine light has appeared periodically for awhile now, flickering on and off till the point where it just didn't go away at all. Replaced o2 sensor with a VT one and it solved the problem for five mins.. Checked tje temp sensor and all is fine but the engine light still visits me, no misfires though...