Front O2 sensor heater resistance

[ASt85]

In my experience even if it is even "slightly" off you'll encounter problems - the only working solution I found to achieve normal running without the Volvo OEM price hike, was to buy one from an approved Denso supplier, you'll find them listed on the Denso web site, and get an identically numbered Denso sensor.

[davebb]

Originally Posted by tony1968

Yeah, that's the page I was looking at. I thought it was a way off because the spec states a 10% tolerance, mine's about 70% over. My hot measurement (well, taken within seconds of stopping the engine) is 100% over.

On the other hand I agree it's only 1-2 Ohms over, I just wonder if the ECM thinks it's to far out and that's why the error keeps coming back.

I'm also puzzled that when I read live data the resistance remains at a steady 2.32 Ohms, yet the current starts high and drops as expected so it's managing and measuring that.

Wife thinks I should give in and take it to a local garage. I think that without Vida they'll be in a worse position than me and will just start fitting new bits until the code goes away.

So, if the sensor resistance is OK and I've proved the circuit is operating when it should and capable of supplying enough current what else can I check? I did remove and reseat the ECM so I could check for corrosion etc and in the hope that sometimes that sort of thing helps!

Hi Tony
What is the resistance of the test leads ? remove this from the reading
Dave

[tony1968]

Turns out that not only was the sensor I bought a pattern part, shipped by mistake in place of the genuine one I ordered, it was the wrong sort too.

I have another on it's way now so won't touch this until it gets here and the first thing I'll do is put my meter on it.

DaveBB, to answer your question my meter's not sensitive enough to pick up any resistance in the leads. I get the same reading direct from the sensor or from the ECM socket. If you're referring to the meter leads themselves I get Zero. Still don't understand the 2.32 reported by the ECM though. Perhaps if this is a default value used when the actual resistance is so far out it detects a fault?

I'll post here again when the new part arrives.

[tony1968]

I said I'd post when the new sensor arrived but didn't get around to it immediately - although it took a week to arrive anyway!

New one came in a box marked "Denso" and with the logo on the sensor itself. Installed it and Vida immediately started showing an actual resistance. Reset the DTC and it's stayed off this time. Ebay seller has refunded my original purchase so happy all round.

LTFT still a bit high in sectors 3-5, although I changed the fuel and air filters yesterday so that might make a difference. Not enough to raise a DTC and car runs fine so I'll not worry about it.