Oxygen Sensor Heater Circuit Question

[anonymous-user]

The initial message was deleted from this topic on 21 August 2025 at 21:24

[eliot]

02 sensors dont work very well when cold, so the heater is used to get it up to temp whilst the engine warms.
It you bypassed it, it may clear the heater fault but you may get other o2 related errors because it will be giving out odd values.
Why not simply replace it - they are not that expensive?

[stevieturbo]

MUDGUTZ said:

Hi, I have a Lexus GS 300 with P0135 & P0141 fault codes (O2 Sensor Heater Circuit Bank 1 Sensor 1 / 2)

I was thinking, before I go ahead and replace these, as it's only the heater circuit in each sensor that has failed (verified by fault codes and checked with a multimeter as open circuit), could I just join the heater circuit wires up to fool the ECU and clear the fault code?

I've heard about O2 Sensor resistance values of 12 Ohm, is this for the actual sensor or the heater? Even if that were the case, could I buy a 12 Ohm resistor from Maplin and put that in?

So you're asking if you can short circuit a 12v and ground wire ?

Mmmmmm go for it.

Or maybe just fix the problem instead ?

[eliot]

I find it slightly unusual that both heaters have failed,unless one failed ages ago and the other has now joined it.
The heaters are there for a reason - bypassing them is just being cheap - £100 for a pair isn't that bad in the scheme of car borkage.

[Steve_D]

Last o2 sensors I bought were £11 each.

Steve

[stevieturbo]

eliot said:

I find it slightly unusual that both heaters have failed,unless one failed ages ago and the other has now joined it.
The heaters are there for a reason - bypassing them is just being cheap - £100 for a pair isn't that bad in the scheme of car borkage.

Or it's a broken wire feeding both sensors.

Again, best to fix the problem, instead of bodging or guessing.

[stevieturbo]

MUDGUTZ said:

I've put a multimeter on both sensors on Bank 1: checking the wires that go to the heater circuit at the sensor plug (the ones that are the same colour) they both (both Sensors) indicate open circuit. If I were to put the multimeter on the socket, any ideas what the amps should be? Maybe that would rule out a break in the heater circuit wire that is common to both sensors. BTW I've received a quote from Lexus for replacement using Toyota sensors:

1 x Oxygen Sensor £160.33 + VAT
1 x Oxygen Sensor £153.10 + VAT

1.4 hours Labour @ £80.00 per hour £112.00 + VAT

Total £425.43 + VAT
Total Inc VAT £510.52

if you put them on the socket, there would be no amps, because that isnt what you would be measuring.

Clearly you need to check for 12v and ground. If you have a clamp meter or wish to connect an ammeter in-line with either of thsoe two wires, then yes you would hope to see current flow, but as the ecu is already telling you there is not and there is a fault with the heater circuit...not really a lot of point in doing that.

Likewise replacing sensors when the symptoms and information to hand isnt suggesting sensors are faulty...is a bit silly.

And whilst cheap aftermarket sensors are never great, £72 each is a tad cheaper

If you're able to unplug and poke at the sensor as you're already doing, changing them really shouldnt be too difficult that it would ever require a dealer.

http://www.ecolambda.co.uk/main/lexus.htm


But no point buying sensors until the fault has been diagnosed correctly.