O2 sensor Heater Element Nightmare

[MattGZ]

Any help will be greatly appreciated.

I have been getting an error code for BANK 1 SENSOR 1 HEATING ELEMENT and have gone ahead and changed the O2 sensor. Not an easy job as it is located in a very cramped space. After Brand new Bosch sensor installed and code erased car ran fine but still gave the error.

I decided to change the sensor again with an original Renault one, used but in A+ condition. Car is running better than ever and MPG are back to normal. Unfortunately the code is still been shown and on startup there is a bit of rough idle when the ECU checks the heater element, then again after a couple of miles. After that time car runs perfectly.

Having gone through 3 sensors and after checking all of them for resistance on the heaters with a multi meter and getting around 9OHMS I am guessing the problem is elsewhere.

I have spoken with 3 mechanics and got the old "never buy a french car" and how the electrics are a nightmare and none of them wants to go near it.
I was wondering if anyone else had had this problem and if it can be a blown fuse, as I am guessing the heater must pull quite a bit of current on startup and might have a dedicated fuse. I have consulted multiple documents, my Haynes manual etc. and could not be pointed in the right direction.

I would greatly appreciate any help.

Car is a Megane CC 2007 Petrol 1.6 VVT

Thanks in advance.

[quaker@eircom.net]

Hello there,
I see you checked the resistance with a voltmeter. Now I assume when starting from cold the o2 heater should be turned on. So get the meter and go across the two heater wires with the meter on dc volts ( 20v scale) and you should get a voltage reading of approx 12-13 volts. Also not sure do you need to reset the code on repair.
rgds
Maurice

[q292u]

I think you need to clear the error code as well as changing the sensor.

[MattGZ]

Hi. Thanks for the quick reply.

I should have probably mentioned this before but I have cleared the codes several times and tried even resetting the ECU by disconnecting the battery. They go for a while but remain as pending codes and come back after 2 or 3 drives.

I will try testing the harness with the Multimeter again as last time I did not get a reading and assumed that the probes were too thick (which they are) and were probably not reaching far enough.

If I do not get voltage (I am seeing this as a string possibility) I would assume either a bad connection or a blown fuse. Does anybody know which fuse feeds the heater?

Thanks again.

Matt

[quaker@eircom.net]

Hello there
I assume you checked the original O2 sensor for heater continuity.
The power feed for these heaters can be different.
It can be a direct B+ ( via a fuse over a relay contact) feed and then the other end is earth pulsed under control of the ecu.
It can be a full earth and then the other end is power pulsed under the control of the ecu.
Try to turn on the ignition and see what conditions you get on the 2nd O2 sensor..it is usually a four wire type.
You should get a B+ ( or a full earth ) on one of the heater wires and the same on the other wire by reason of the heater continuity.
Now compare these conditions to the 1st O2 sensor.
Also see what DTCs are present. It could be a fuse as you say...I looked at the Haynes manual but saw no reference to O2 sensor power feeding.
rgds
Maurice

[MattGZ]

Hi Maurice. Thank you very much for your helpful message.
I must admit I am a little lost as to how to check a B+ on the sensors. I have a multimeter and Torque Pro but I am a little confused as to how to check this.
I do however gather from your reply that the heater element of both sensors would be controlled by the same relay or fuse and for that reason by checking the post cat one I can narrow down the culprit to the wiring in the front.
I have also chequed the haynes manual and all documents I have at hand and there is no detail as to where the fuse is located.

thanks again
Matt

[quaker@eircom.net]

Hello there..B+ is battery positive ( +12v)
turn on the ignition first....I assume its a key card in a slot so put in the keycard and NOT tipping any pedals, press(and hold) the start button for approx 5-6 seconds and you should hear the ignition relays turning on ( the dash lights up as well ).
If the feed to the O2 heaters is +12v when the ignition is switched on, then use the multimeter to probe both heater leads at a suitable connection ( by back-probing)...this should prove something and also compare to the post cat O2 sensor.
To turn off the ignition, pull out the keycard and press the start button two times quickly.
rgds
Maurice

[MattGZ]

Hi again Maurice.

Thanks for your help. I suspected that was what I needed to do. I will probably give it a shot over the weekend and let you know how it went.