As with the last thread I had to start, I've researched and researched till I'm blue in the face. I have tested all I can (comfortably) test and I caint test no more.
My service engine light came on about a month ago and the display reads Fuel Fail 69. As far as I can tell, there has been no change in the running of the vehicle in any way. I don't have to "mess" with the gearshift (its condition seems unchanged), I have not had to jump start the car, and it does not have any other electrical issues. I have tested battery voltage with car on and off. At one point I put a trickle charger on it which turned the light off for about 10 miles which made me think it was the battery or alternator failing. I then removed and cleaned both battery cables and terminals. This raised the static voltage from 11.5 to 12.2 but did not turn the light off even though the ammeter in the car reads 14 volts running which agrees with my voltmeter. I am unsure how or where to accurately test the rotary switch and I have checked for a vacuum leak albeit somewhat superficially.
The code itself calls for bad rotary (neutral safety) switch. I have found electric diagrams for its plug showing what voltage for each gear selection. I have also found suggestions that low battery voltage will set the light off. And..... now I've found a questionable listing suggesting a vacuum leak will cause it.
In my reading it was suggested that the switch is touchy to adjust when replaced and so I don't want to dislodge it until I must. Can anyone tell me how or where to run a test on the switch and maybe how to readjust it once it has been removed?
Thank you for your participation in this matter.

 

Hi Jerry,

There is a diagnostic flow chart for DTC 69 in the Engine Management manual, which you can download here:

http://www.jagrepair.com/images/Elec...tems%20S91.pdf

One possibility is that your transmission cable has stretched.

The rotary switch might need to be cleaned or the solder joints reflowed. Some photos can be found here:

Welcome to Jag-lovers - Members Photo Viewing Page

I think the decoder module in your '92 is different than the one in our '93, but just in case, some photos of ours can be found here:

Welcome to Jag-lovers - Members Photo Viewing Page

It might also be worth cleaning the main transmission electrical connector:

Welcome to Jag-lovers - Members Photo Viewing Page

For some reason, I think I may have once resolved a FF69 by cleaning the engine bay ground points, but I could be wrong. But it might be worth checking the Electrical Guide for any ground points used by the ECM or TCM.

There is also an excellent transmission diagnostic procedure in the Jag-Lovers XJ40 eBook for diagnosing Limp Home Mode, but it includes voltages and resistances and such that should be present at the TCM electrical connector that might help you rule out an electrical problem there.

Cheers,

Don

 

Not had this problem Jerry but if you haven't re-flowed both footwell fuse boxes I'd definitely give it a shot!

It's a a reasonably quick/clean/accessible job that can sort out multiple issues on our cars, especially the ones that spend winter at our latitudes ..

Larry

 

Sheesh Don. That's...... exactly..... what I was looking for. Maybe if I remembered to breathe while searching I could last longer before turning blue in the face. I don't know what the (my) problem is, but I always have difficulty finding things online. I was searching "ff 69" and "fuel fail 69." It never occurred to me to search DTC. Duh. Anyway, I took that gravel shield off and looked at the switch (to confirm it was still there apparently) but I didn't think to take the switch apart on the car. again, Duh.
Is supposed to rain most of the morning so I'm not sure I am going to bother with the car show. We shall see what the boss says. Ill look at the switch first and then proceed to fuse boxes if need be (again thanks Larry).

 

Got the car into position and set it up on jack stands . Took the cover off the switch and found ..... Wait for it....... Nothing. No appreciable wear. No dirt. I suspect a replacement used part would be worse than this. By the way, it's past 178000 miles. I will use eraser and 'electric cleaner anyway, but I promise I'll be as surprised as the reflowing of the fuse box in the other car if it works. I am leaning towards a worn starter causing excessive voltage drop on start up. But. We shall see.

 

Hi Jerry, always a disappointment to find a clean component when looking for a duff one, eh?

I just reviewed Don's pics on the switch and he suggested this possibility:

I know when I did my fuse boxes, I looked at them and they looked so clean I refused to believe there was a cracked joint but after taking them apart a THIRD time (after exhausting all other possibilities) of course I found the sneaky little cracked solder joint.

anyway, keep on keepin' on

Larry

 

I agree. It's very counterintuitive, but when you're looking for a problem you want to find one. In any case, I unhooked battery, flowed those joints, did the eraser thing, rinsed liberally with electric cleaner, checked progress - with switch cover off (Doh!) - of course failed. Reset battery again, reassembled switch and light is out..... Fingers crossed!

 

And in conclusion! Took the car for a spin yesterday of about 20 miles. Drove it to work today. No light. I am calling it fixed. Thanks yet again Don and Larry both.
By the way- Yes, I am stunned.

 

Yay!!!

Larry