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Hi there,
Had a strange one yesterday. THP155, 2011 DS3 DSport.
I was cruising down the motorway between Sydney and Bowral (Australia). It's basically a slow climb from Sydney to the Southern Highlands.
Anyway, on cruise control at 110km/h (approx 70mph) when going up a particularly steep hill, the car suddenly started slowing down. This was about an hour or so into the 1hr 20min journey.
By the time I got to the top of the hill I was in third trying to maintain anything above 90km/h. I thought I was back in my old '73 Corolla from 30 years ago.
No messages, no warnings, no engine light.
When I finished the trip I stopped and checked under the bonnet for anything obvious. With the car shut down, no engine fan running and on restart no check engine light or warnings - but obviously no boost!
Got out the trusty Diagbox when I got home and there are four faults in the ECU:
P0171 (mixture regulation fault: mixture too lean)
P2191 (mixture regulation fault: mixture too lean)
P0133 (upstream oxygen regulator signal fault: ageing or coherence)
P0134 (Upstream oxygen regulator signal fault: no signal)
The first three occurred at around 110km/h at 2343rpm, so pretty much when I noticed it slowing down up the hill, I guess.
The last (P0134) occurred at 0km/h and 926 rpm (and in closed loop mode), so perhaps after the restart? I think it relates to the oxygen sensor heater circuit, somehow.
Anyway, they were all temporary faults and cleared straight away, returning my car to its normal, full boost behaviour.
Hasn't re-occurred in my driving since then (even from a cold start overnight) and everything is normal.
I plugged in the ancient ELM327 and I got a LTFT of -1.6%, which is a bit lean but suggests it's probably not a timing issue.
Would I be right in assuming the upstream oxygen sensor is on the way out? Perhaps a weak signal?
I realise this forum isn't frequented much these days, but there's no way I'm going to write this essay on Facebook!
Any takers?
Regards,
SLC
Had a strange one yesterday. THP155, 2011 DS3 DSport.
I was cruising down the motorway between Sydney and Bowral (Australia). It's basically a slow climb from Sydney to the Southern Highlands.
Anyway, on cruise control at 110km/h (approx 70mph) when going up a particularly steep hill, the car suddenly started slowing down. This was about an hour or so into the 1hr 20min journey.
By the time I got to the top of the hill I was in third trying to maintain anything above 90km/h. I thought I was back in my old '73 Corolla from 30 years ago.
No messages, no warnings, no engine light.
When I finished the trip I stopped and checked under the bonnet for anything obvious. With the car shut down, no engine fan running and on restart no check engine light or warnings - but obviously no boost!
Got out the trusty Diagbox when I got home and there are four faults in the ECU:
P0171 (mixture regulation fault: mixture too lean)
P2191 (mixture regulation fault: mixture too lean)
P0133 (upstream oxygen regulator signal fault: ageing or coherence)
P0134 (Upstream oxygen regulator signal fault: no signal)
The first three occurred at around 110km/h at 2343rpm, so pretty much when I noticed it slowing down up the hill, I guess.
The last (P0134) occurred at 0km/h and 926 rpm (and in closed loop mode), so perhaps after the restart? I think it relates to the oxygen sensor heater circuit, somehow.
Anyway, they were all temporary faults and cleared straight away, returning my car to its normal, full boost behaviour.
Hasn't re-occurred in my driving since then (even from a cold start overnight) and everything is normal.
I plugged in the ancient ELM327 and I got a LTFT of -1.6%, which is a bit lean but suggests it's probably not a timing issue.
Would I be right in assuming the upstream oxygen sensor is on the way out? Perhaps a weak signal?
I realise this forum isn't frequented much these days, but there's no way I'm going to write this essay on Facebook!
Any takers?
Regards,
SLC