Hi just got a P1646 Error Code pointing to Oxygen Sensor. Which Sensor would that be and where is it located? Please need my Texas Emmisions done next Week and need to have this Fixed.

Thank you

 

According to my source, P1637 says : "Fuel Pump 2 (SC) relay malfunction" - that's from Alldatadiy. If you don't have an XJR, then that wouldn't apply, maybe somebody else has seen this.

 

Jimmy its a 1646 i have

 

My bad ... I meant P1646 - same definition. It also says "limits engine speed to 3000 rpm".
Do you get a restricted performance light ?

 

Nope mine is running fine. I have the check engine light on but the Car runs like a charm. When i ran the Diag it came up with P1646 and the P1111

 

The DTC changed for later engines- JTIS defines this as

P1647 ECM HO2S control malfunction –B bank, upstream
– Inhibits B bank upstream HO2S operation
HO2S heater failure
HO2S sensing circuit short circuit to ground or high voltage
HO2S sensing circuit open circuit ECM failure.

Which means the B bank (US drivers side) upstream sensor heater circuit malfunction. I would test the heater voltage at the sensor, then the heater resistance before replacing the sensor.
According to the JTIS reference above, the fuel trim is disabled, so I suspect you will see performance and gas mileage improvement if it is fixed.
P1111 only refers to the drive cycle status- Dont worry about it.

 

Ross

So are you telling me that a 1646 changed to a 1647? Also how would i test it and where exactly is the Upstream Sensor located?

 

No! My bad-
My senility is showing. P1646 is A Bank instead of P1647 which is B bank- so what I wrote applies, only for passenger side. Sorry

 

Sorry for the conflusion. I'm sure Ross must be correct. You can't always trust Alldata I guess. The upstream O2 sensor is near where the exhaust manifold connects to the downpipe before the catylitic convertor. The downstream O2s are after the cats.

 

Jimmy:
I have found that if you look at Alldata, compare it with whats on here, and with JTIS - and it all matches, you MIGHT have the right information. But is sure is a crap shoot. For instance, the discussion on a bunch of threads over the last several months about cylinder numbering, which you would think should be pretty straightforward. Also, with JTIS, you need to look at the first year of a particular model or engine series as well as the year in question, and be careful to note the vin numbers after a search. As an example, if you search MY 01 for DTCs the JTIS search results will show the results starting at MY 98 but will give VIN number ranges.

 

You're right about the crap shoot Ross. I have also found that in Alldata my Disco has a distributor, but the one in my driveway has coil packs. Maybe it was a changeover year ? The stuff about the cylinder numbering - wow, could numbering 8 cylinders be more confusing ?

 

OK my friends. What a Trip. So i was able to replace the upper O2 Sensor. Not an Issue. The lower O2 Sensor is Hell tried to use a O2 Sensor Socket and was not able to get it out!!! Any Tip or Tricks on how to get to it? And let me ask Bank 1 is the Passenger Side RIGHT. Thx for the Help on this ya all

 

You can try penetrating oil, or heat the bung with a torch. And yes, Bank 1, or "A" is passenger side (US).

 

I was able to remove the OS in the cat with a thinwall OS socket. the 1st one I bought would not fit inside the Bung. With the right socket, and some PB Blaster, it came out but it took a long breaker bar. I had the luxury of removing it them with the cats out of the car because I installed new high flow cats from Nameless Performance

 

Good morning. Getting the P1646 code on our 2001 XJ8 with Restricted Performance light (nothing flashing).

I removed that plastic top center cover, the one up against the firewall, and looking straight down on the passenger side, the O2 sensor causing the P1646 is right there coming off the manifold and terminates with a gray plug? There is another sensor directly below that one that looks to be more difficult to get to.

My question is this. Can I test the sensor with a multimeter in some way before I purchase a new one? How do I know this particular sensor is the defective part? There are 4 sensors, 2 upstream and 2 downstream on each side. I hope I don't need to replace one on the drivers side. Looks to be buried pretty good.

I've read all the previous posts , and thank you to all. It helped a great deal already. And forgot to add...when I took off the plastic cover, it has a half turn common screw head fastener. Well.....the bottom half fell off. There is a tab it secures to. Maybe just add a nut plate there.


Thanks, Tim