Good day Gents!
About 2-3 months ago, my car started going in limp mode. It
would sometimes go away with stopping the car and simply
restarting. Other times it would not go away at all.
The transmission appears to have enough fluid. It looks to
be towards the max level when warm. I do not know when the
last fluid & filter change was.
I cleaned the throttle body in December of 2009. The
problems didn’t start until 2010.
About a month ago, I drilled a hole in the Throttle Position
Sensor and sprayed electrical contact cleaner inside several
times. It behaved a little better, but not majorly.
The voltage for the TPS was about .6 at both contacts before
I did this. I have not checked it since.
I opened up the plug for the connection to the TPS. I took a
small round file and cleaned up the inside of every female
plug. I removed each male pin, one at a time, and ran a
small file over them as well to make sure I had a good clean
surface. I sprayed them both with electrical contact
cleaner, then WD40 and put it back together. It has worked a
LOT better since then. I thought it was solved. It worked
for 2 days and then I had limp mode again.
A week later, I jacked the car up and opened the rotary
switch on the transmission. I sprayed that with cleaner. I
didn’t notice any corrosion or damaged areas. The round
connector was checked and looked fine. It worked for a day
or two and I’m back to random limp modes again.
This weekend, I attacked electronics under the dash. I
pulled the purple relay mounted on the right blower motor,
that looked nice and shiny. I removed the transmission
decoder module on the back side of the relay rack panel (far
right side). I opened that box and did not notice any
corrosion or damage. I sprayed the components and the plugs.
Next stop, check the TCM. The car was dead cold and sat
Pin #19-># 5 was 37
Pin #19->#24 was 37.4
Pin #19->#42 was 37.6
This is not the 34 ohms mentioned in the XJ40 online book,
but seemed close enough to not be an issue.
Pin #19-># 6 was 6.2 (within the 5-7 range)
Pin # 2->#38 was 337.4 (a touch higher than the 300 +/- 10%,
but seems reasonable)
Pin # 7, # 9, & #26 all showed .000 to ground/earth.
Pin # 1 & #39 had 12v
Sprayed the connections and put it all back together.
Removed the ‘Sport’ switch by the gear shifter. Opened it up
completely - right down to the circuit board. Sprayed that
with cleaner and reassembled.
Connected the negative battery cable (was off for 2-3 hours
for all this) and started it up. Drove around for about 45
minutes with no problems at all whatsoever. I did local
street all the way to highway speed and back. No limp mode.
I drove to work this morning (less than 15 minutes away) and
I drop into limp mode as I make a right turn into the
Why am I still getting random limp modes?
My next guess would be to replace the TPS. I’d rather not
throw $250 at a guess. Can anyone see anything I missed, if
my numbers were bad, or what to look for now?–
1991 XJ6 (XJ40) Sovereign - 137,000 miles
Oyster Bay, NY, United States
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