Sensors...

RavenMocker

Well-known member
Jul 25, 2015
45
4
PNW
I’ve been troubleshooting some issues with my 2000 Discovery 2. The two I’m stuck on are a massive evap leak and Oxy Sensor Heater Downstream Cat Bank 1 Drive Cycle C.
I think the evap leak was being caused by the EVAP canister vent valve WTY000020. Same part as the ACDelco 214-1091. I pulled the part to test it. It was a little sluggish closing and opening. I cleaned it and then it worked like a solenoid is supposed to. But when I’d try and pass air thru it when closed it would leak. So I looked inside and found the coil spring that pushes the valve back open was bent enough to allow one of the coils to get between the valve and seat which created a leak. I did the repair and tested it again. This time zero leaks. So far the truck has been happy as I’ve yet to throw another evap massive leak code. I pray it stays that way.

The O2 sensor is a completely different issues. I’ve replaced all four O2 sensors. Graphing both the input and output O2 readings showed the cats are working. Yet even after the replacements I’m still throwing this code. I’m stuck and could use some help.
 

Flyfish

Well-known member
Oct 29, 2004
1,260
140
50
St. Louis
Have you tried a temp gun on the cats inlet and outlet temperatures to verify if it’s working properly?
 

discostew

Well-known member
Sep 14, 2010
6,738
636
Northern Illinois
The o2 heater fault should be easy. It has a heater to get it to operating temp faster. 2 of the 4 wires to that sensor are 12 volts and ground for that heater. It will only be on during warm up. I would look close at the wires in that connector and see if one wire is backing out of the plastic connector Body.
 

RavenMocker

Well-known member
Jul 25, 2015
45
4
PNW
The o2 heater fault should be easy. It has a heater to get it to operating temp faster. 2 of the 4 wires to that sensor are 12 volts and ground for that heater. It will only be on during warm up. I would look close at the wires in that connector and see if one wire is backing out of the plastic connector Body.
Ill check that today.
 

RavenMocker

Well-known member
Jul 25, 2015
45
4
PNW
What’s the actual code you’re getting for the O2?
I’m using the iLAND diagnostic tool. The actual P codes aren’t shown. Or it’s not showing how I’ve it setup. But the actual code is posted as, “Oxy Sensor Heater Downstream Cat Bank 1 Drive Cycle C.” This was being thrown before I installed new O2 sensors and still it remains. As listed above I graphed the inlet to both cats and then turn rear outputs. The graphs show the Cats are doing their jobs.
 
Last edited:

Flyfish

Well-known member
Oct 29, 2004
1,260
140
50
St. Louis
I’m using the iLAND diagnostic tool. The actual P codes aren’t shown. Or it’s not showing how I’ve it setup. But the actual code is posted as, “Oxy Sensor Heater Downstream Cat Bank 1 Drive Cycle C.” This was being thrown before I installed new O2 sensors and still it remains. As listed above I graphed the inlet to both cats and then turn rear outputs. The graphs show the Cats are doing their jobs.
I was just thinking if the sensor is throwing a code that the signal is out of range, the graph info may be questionable. But I may be completely wrong.

Regardless, make sure the wires aren’t rubbing on something. I’m guessing the fuse is fine, F2 I think. Also, maybe swap sides on the rear O2’s and see if the code changes to bank 2.
 
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discostew

Well-known member
Sep 14, 2010
6,738
636
Northern Illinois
I was just thinking if the sensor is throwing a code that the signal is out of range, the graph info may be questionable. But I may be completely wrong.

Regardless, make sure the wires aren’t rubbing on something. I’m guessing the fuse is fine, F2 I think. Also, maybe swap sides on the rear O2’s and see if the code changes to bank 2.
Not for a heater fault. I bet its the heater circuit. And whats the chances that both those o2 sensors are going to come out of those pipes to switch sides?
 
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Flyfish

Well-known member
Oct 29, 2004
1,260
140
50
St. Louis
Not for a heater fault. I bet its the heater circuit. And whats the chances that both those o2 sensors are going to come out of those pipes to switch sides?
Since he said they were new, it shouldn’t be too difficult. At least unplug the bank 1 sensor and make sure the harness plug is in good order.
 

RavenMocker

Well-known member
Jul 25, 2015
45
4
PNW
Both sides O2 inputs were ok prior to replacing. But the rear O2’s were getting old and the signals were still ok but you could see they were not going to last much longer. So I replaced all four O2 sensors. The front graphs actually read better with not as much noise. The rears smother out allot. To the point you could tell both cats are working. If I could put it another way... on a scale from 1 to 10 with 10 being the most out of spec... prior the rears were about an 8.... after replacing they went down to a 1.
 

rovercanus

Well-known member
Apr 24, 2004
9,518
172
What sensors did you use? I got some one time that threw a heater circuit fault. Contacted the vendor and he sent me two more that did the same thing. Some cheap ass sensors just don't work.
I use the bosch originals. Some people have said they had problems with them and went with NGK but I think they have mommy issues.
 
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