Ax - Engine management warning light

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Jaf
Posts: 514
Joined: 09 Dec 2010, 19:17
Location: Oria, Spain
My Cars:
x 29

Ax - Engine management warning light

Post by Jaf »

So..the car is a 1994 1.1 petrol MMG62. The Spanish MOT people say the Engine management light has to be off. I have found "Permanent Fault Mixture Adjustment" with my Lexia. The light has been on for 2 years with a well running car (except fast, sharp right hand turns where she tries to stall), CO good - passed 2 MOTs.

Testing the CO with my old meter I had 0.3 with the light on and 2.2 with the light off. Then added some cleaning additive, went for some hard drives. CO with light off is now good but the idle is a bit low. However the Engine management light keeps coming on, varies between a couple of minutes and 20 minutes at tickover.

The Lexia does show one odd thing, the Idle actuator shows 80% if I clear the fault with the Engine running. A blip of the accelerator brings it back to around 20%. Should I only clear faults with the Engine off? Should I try disconnecting the battery, would that reset the ECU?

Anyone know what "Permanent Fault Mixture Adjustment" means, or have any suggestions?

Thank you.
Fred, a silver 1998 1.9TD SX Xantia.
Gwin, a white 1994 1.1 AX.
wheeler
Posts: 6848
Joined: 21 Sep 2002, 19:07
Location: United Kingdom
My Cars:
x 717

Re: Ax - Engine management warning light

Post by wheeler »

with the engine fully warmed up can you see what the oxygen sensor is doing on live data ? It should constantly fluctuate between 0.1v & 0.8v
Jaf
Posts: 514
Joined: 09 Dec 2010, 19:17
Location: Oria, Spain
My Cars:
x 29

Re: Ax - Engine management warning light

Post by Jaf »

Thanks.

I took 3 photos. Seems to be constantly 0434mV. What do you think?

Can check tomorrow for live data.
Last edited by Jaf on 24 Jan 2017, 22:13, edited 1 time in total.
Fred, a silver 1998 1.9TD SX Xantia.
Gwin, a white 1994 1.1 AX.
Jaf
Posts: 514
Joined: 09 Dec 2010, 19:17
Location: Oria, Spain
My Cars:
x 29

Re: Ax - Engine management warning light

Post by Jaf »

Aha. Have read a little more about the Oxygen sensor. It appears if the value is stuck it must be replaced. Did check ohms and heater part works, but didn't know about voltage fluctuations. Yay! Will check tomorrow.
Fred, a silver 1998 1.9TD SX Xantia.
Gwin, a white 1994 1.1 AX.
Jaf
Posts: 514
Joined: 09 Dec 2010, 19:17
Location: Oria, Spain
My Cars:
x 29

Re: Ax - Engine management warning light

Post by Jaf »

Thanks again wheeler. Changed the oxygen sensor and the Lexia shows the voltage fluctuates properly now.

Passed the MOT!
Fred, a silver 1998 1.9TD SX Xantia.
Gwin, a white 1994 1.1 AX.
wheeler
Posts: 6848
Joined: 21 Sep 2002, 19:07
Location: United Kingdom
My Cars:
x 717

Re: Ax - Engine management warning light

Post by wheeler »

Result !
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