scott-UK

Hi, I'm having problems with my Fiesta with a lack of power and the engine management light turning on and off!!

I took my car to a friend with a diagnostics kit and it showed the following codes:

HO2S-11 (Heated Exhaust Oxygen Sensor Right Upstream) Circuit Slow Response
System Too Lean Bank 1
HO2S-11 (Heated Exhaust Oxygen Sensor Right Upstream) Circuit Malfunction
Invalid fuel tank level message from instrument cluster
Knock sensor 1 circuit malfunction
HO2S-11 (Heated Exhaust Oxygen Sensor Right Upstream) Circuit Slow Response

I changed the Oxygen sensor back in 2014 - Could this have gone already?

I would be extremely grateful for any advice anyone may have for me!!

oldford

I would be looking at the mixture the engine gets. It seems to be lean.
OR you have a leak in the first part of the exhaust near the oxygen sensor.

What's your fuel consumption doing? Same, higher, lower?

scott-UK

OK thanks, may sound slightly stupid but I'm new to this - How would I test if there's a leak?

I would say it's about the same.

oldford

Start the engine, block the end of the exhaust and without a leak the engine should stall.
With a leak the engine keeps running and you should be able to hear where it leaks.

But with the fuel consumption being about the same, I would say the cause is something different. Maybe a leak somewhere around the inlet manifold or a defective sensor.

Can your friend read live data? Then check the "Fuel Trims".
They should be close to 0%.

vrum-tss

what brand of sensor did you use? i wouldnt recommend anything other than a bosch one. if its a cheap'n may well have gone again,

other possible causes, expended or blocked CAT (do you notice any bad smells coming from the car?) , possible wiring malfunction

did he clear the codes and retest? or just a single test, i would clear and retest as it eliminates previous faults that could have been cured and still recorded.


my neighbours fiesta had a lack of power issue, turned out to be blocked CAT causing backpressure in the exhaust system and making it run bad , check all the basics, plugs fuel filter etc, does it misfire? blocked cat could explain the lambda sensor reading bad

scott-UK

Hi,

Problem was the Lambda sensor! Orignal sensor I used was HAAS - Must have been faulty!

I've now replaced with a NGK sensor and its worked a dream!!

Thank you both for your replies, much appreciated.