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Power resistor and FF44 error

Steve DAngelo
*

forum user since 2003-09-21

 

I was thumbing through my XJS maintenance manual and I found
on page # H12, fiche 3, the power resistor and the heated O2
sensor are on the same page. What is their relationship and
could my FF44 code be caused by a faulty power resistor?

1994, XJ-S, 6.0 liter, Coupe

Power resistor and FF44 error

Andy Simko
ember At Large *

forum user since 2006-02-22

 

Steve, aren't most O2 sensor problems actually a bad O2 sensor?
it seems i never get any of our cars in and out of the shop without changing at least 1. (2 or more at a time on my windstar vans)

1995 black xjs 4.0 convertible

Power resistor and FF44 error

Steve DAngelo
*

forum user since 2003-09-21

 

Andy,
First thing I changed out.
They also seem to be functioning.
It's an issue I have had for about three years.
There is a long list of things I have replaced or checked.
No one had suggested that it could be the power resistor but since it's on the same page as the O2 sensor I was wondering what connection they have if any.
My printer is down so I can't print any of the wiring diagrams.
Thanks Andy,
Steve

1994, XJ-S, 6.0 liter, Coupe

Power resistor and FF44 error

Steven Petry
Jaguar Association of Greater Indiana *

forum user since 2007-02-03

 

Steve,
The power resistors really couldn't have anything to do with your code 44......UNLESS, you have an accompanying performance degradation. Since you have changed out the O2 sensor, you need to find something that is causing the O2 sensor signal to go high or low and set that code. The code is for the "A" Bank sensor, which is he RH bank as viewed from the driver seat.

The power resistors are there to limit the current the ECM is switching when it fires the injectors, they're there to protect the ECM driver transistors. If one of the power resistors failed, three injectors would not be firing correctly and would cause a poor running engine, noticeable for sure.

Other things to look for are no power or ground to the O2 sensor heater on that side. The single wire is the signal to the ECM, the 2 wire connector is the power and ground to the heater; no heater, poor O2 sensor performance and Code 44. Also look for a vacuum leak on that bank, an air leak drives the O2 signal low and.........Code 44. Then there is the possibility of an air leak in the exhaust system, like a cracked manifold, leaky doughnut gasket to the catalyst, or possibly even a cracked catalyst itself. Those would let air into the exhaust stream that can be detected by the O2 sensors, again, Code 44.

So now you know why the cause of that code can sometimes be elusive; frustrated many a tech I assure you.

I do have to differ with Andy, though. In my experience the number of times the cause was NOT the O2 sensor, far outweigh the number of times it was.

Good luck!

S Petry
'95 XJR
'97 XK8 Conv.

Power resistor and FF44 error

Andy Simko
ember At Large *

forum user since 2006-02-22

 

steve, i have no specific jaguar knowledge about this, but i know for some cars, when the sensor is changed, some sort of "reset" is necessary to set a base reading for the new sensor.

1995 black xjs 4.0 convertible


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