Hello,

Having sorted out most problems caused by that recent new gearbox instalment in my X308, I keep getting the red engine symbol on my dashboard, indicating
P1647 code (oxygen sensor fault). I can clear that with my new OBD2 scanner, but that does not solve the problem.
Can anyone tell me if it would be a good idea to change all four sensors (two upstream and two downstream) since if one is going on a 17 year old car, I think
that the others may be failing soon too.

Thank you.

 

The upper, heated sensors are a common failure. It would not be a bad idea to replace both of them. I haven't seen anyone reporting failure of the lower ones. I wonder if the transmission shop disconnected the sensor and didn't get the plug seated properly or bent a pin.

Not having removed the transmission from a xj8 I'm not sure if removal of the cats is involved, but when I dropped my xk8 trans. I did so.

 

Yes RJ, the cats on the xj8 need to be removed just like the xk8. It is possible the sensors got damaged on removal. Even if they unplugged the sensors before removal there is the possibility that they missed that the O2 cables are zipped tied to the transmission cooler lines. If they dropped the cats without cutting the zip ties the cats will hang by the O2 cables and the weight of the cats can possibly pull the wires out of the O2 sensors.

 

Once again: I don't find a coincidence, I think the transmission shop bungled some piece (s) of their work. Right side upper is easy replacement; left side upper, lots of work to get at the part, which is the one you are showing as bad. I would examine the wires first, thinking the tranny guys were heavy handed (as Bob noted, above)..

 

Thank you all !

I will now go on by checking the rest of my old car, bit by bit, like for an unexplained vibration that appears out of nowhere when it reaches 85-90 Km/H. Hahaha ...

Takeo.

 

Bad grounds, like partially torn or loose wires, can cause all sorts of issues, especially over bumps and road vibration. Look closely around your throttle position sensor, the oxygen sensor (upper left), and the fuze box (specifically the fuzes that control circuits that control P1647 and P1020, P1021). The P1100 goes away once everything clears. Off chance, look at the grounds in the boot, as well.

 

Hi Jim,

You may be right ! Friend of mine had also a gearboc replaced on a Nissan. Lots of problems were solved later by ust adding a ground strap that lead from the new gearbox to the engine block.

Thanks,

Takeo.

 

I have just rebuilt my 5HP24 and had the same fault code. I believe it happened because the catalytic converters was shaken on removal, disturbing the oxygen sensor that is 20 years old. My wiring is correct. I ordered a new sensor.
I also do not find the left side sensor that difficult to exchange. I did loosen it before I re- installed the Catalytic converter. I have a T30 on a 1/4in flex head ratchet or a T30 bit in a short handle ratcheting tool, either is exceptable. Remove the reservoir, if the PEC tubing snaps, be glad it didn’t happen on the road, replace it. The screws for the shield sometimes are stubborn and sometime have been buggered by previous repairs, that would be the difficulty. I sometime use a punch on the edge of the screw and knock it loose, when it turns it can be turned by hand easily. There is a special socket for oxygen sensors, it is a 22mm and fit deep as to grab the sensor fully. Oddly enough, I have always found the tie rap that hold the wire, a pain.