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another TPS problem

S

SuperRoo

NAXJA Forum User
Location
London, UK (formerly OZ)
Replaced my TPS and tried to set it by back probing. Found I was getting 0.017 volts at the tps (ignition on) so checked the plug disconnected at the opposite end - it too shows 0.017 volts as well. How do I get 5.0 volts? What am I missing? This is the first time I've ever replaced a tps and had to set it. Found excellent stuff from you guys before I attempted this and took the advice from some of you on here and ordered it from chryslerparts, which I might add, gave me excellent service. It hasn't corrected my shifting problem (yet), too slow upshifting from standstill, and giving crap mileage, but since it is not getting the 5volts it needs I can understand these results, other than that, she drives smoothly once I manually shift the auto. Thanks for help in advance

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1988 Cherokee Laredo 4WD, 4.0Litre, AW4,
 
So Peter...I heard you were having problems with your TPS reports...I think we are just gonna have to have you come in on Saturday...yeah...
 
Don't forget. If you leave ignition on for several minutes without engine running, the 5 volts gets shut down from the ECU.
 
cygnus58 said:
Don't forget. If you leave ignition on for several minutes without engine running, the 5 volts gets shut down from the ECU.
Click to expand...

yep, I read about this in someone elses post, so I set the probes up before I switched on the ignition -double checked -tripled checked, I even cleaned up the negative cables terminating on the block (3 I think) next to the dipstick. I ran a lead from the battery negative to the switch to check if it was a grounding problem - it made no difference. As I'm new to all this I'm completely stumped - aaaarrrrrrgggggghhhhhhh:shocked:
 
The XJs prior to 1990 have a main bulkhead connector at the firewall on the drivers side which is called C103. The pins inside this connector are known to build up oxidation over the years if the factory dielectric grease dries out.... This will cause bad electrical connections to different areas in the engine compartment....
Disconnect your negative battery terminal, separate the connector and clean the terminals. Apply some dielectric grease to each terminal... Reconnect the connector... and connect the negative battery terminal....
This should solve your problem.....

A friend of mine is a Jeep technician and he removed the connector entirely and soldered each wire together to alleviate the problem permanently....
 
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yep found it. took the bolt out (right connection) and found black crud which i presumed was the remains of the above forementioned grease. can't yet work out how the left side disconnects tho'
 
just cleaned out as much crud with a screwdriver and cloth as i could -anyone got an easier or better method? Checked the volts again and it's still 0.17 volts! i thought it would of made some difference, I don't have any dielectric grease so I'm off now to buy some. After re-reading my initial post I realised I put one too many zero's in the volts - it should be 0.17.
I checked the flat connector of the tps and i'm getting A-C - 4.79 volts; B-C - 5.03 volts; where C I took as the negative.
Also worked out how to take the right coupling off from my previous post.
 
IF you have the battery ground disconnected.... you can try to use a small wire brush on the male pins and a small round bristle brush on the female ends.....

With those voltages read at the TPS.... ; it looks as though the problem was the oxidized pins in the C103 connector.
 
the input voltage should be around 5v but is usually a little less on a vehicle that is around 20yrs old due to corrosion in the wiring/terminals and is normal.The output voltage should be 17% of the input voltage.
So in your case you have 4.79v input the out put should be set(by rotating the tps)to 0.81

EDIT:Just realized you have an auto...the above applies to a manual,oops.
 
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got down to my local parts shop, spoke to two pathetic drones who argued with me that dielectric grease doesn't exist! and proceeded to show their range of greases...the sad thing is I have seen a small tube/box of dielectric on the shelf there in the past, but not today.
I grabbed some electric contact cleaner spray and disconnected the battery and gave the C103 a good squirt, once it evaporated i put it all back but still no result. I'll have to hunt down the grease from someother place tomorrow.
 
You did say you had 5 volts on 2 terminals at TPS correct?
So, you replaced TPS for shifting problem, right?
Symptom remains.
When you say "manually shift" do you mean with TCU fuse pulled?
The AW4 TCU uses TPS voltage, and Speed input pulses from the speed sensor in the output of the transmission for the gloriously reliable and smooth shifting that it does so well. . Maybe the wiring for (connectors, etc.) or the transmission output speed sensor is giving you a problem. Not sure how often they go bad but they are a simple reed switch IIRC. I've seen them fail in older satellite dish actuators. (i think they usually stuck closed) I saw a recent thread on testing, but it wouldn't be easy without an oscilloscope on board.
Of course, it could be mechanical.
And if your voltage doesn't change at all at 2 TPS connectors with throttle position, you may have installed the TPS with the actuator beyond the contact with throttle.
That would only compound matters but it should behave quite differently from when you started.
 
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The TPS on the TCU side gets its voltage from the TCU. Check the TCU fuse, in line fuse to the left of the TCU! Then check that the TCU is connected to the harness. Then if that fails, check the TCU voltages (PM me your email address), and then follow them to the TPS.
 
To cygnus58, I replaced the TPS because 1) wasn't shifting from rest -more like a worn manual clutch feeling 2) exceesively bad fuel economy, around 8-10mpg. After reading the numerous threads on here I came to the conclusion it had to be the TPS...besides it was more than likely 20 years old anyway.
As to manually shift, I physically shift it to 1-2 position to start from rest, then physically shift to 3 then D position - i never touched the fuse.
To Ecomike pm sent.

Thanks again to everyone for your ideas and suggestions. I've got to take her for her annual test on Saturday and I'm back at work tomorrow:bawl:
 
Check the fuse, it could be your only problem
 
Well, the jeep passed her roadworthiness yesterday, so she's good for another year.:cheers:

Thursday evening I checked the fuse and it was fine. After remembering having read numerous posts of fuses which "looked" OK, but apparently weren't, I decided to change the fuse - I received 4.71v at the TPS. Not quite 5.0v, but enough to get me sorted for the time being...any suggestions on where the rest of the voltage has gone to?

Couldn't find dielectric grease anywhere, the electronics shop sold me "silicon grease", as when he typed in dielectric on his computer, silicon came up. The tube says - "high electrical insulation, waterproofs/repels moisture, high temperature resistance; ...smooth, non-melting for high surface resistivity & excellent resistance to tracking & arcing".
So would this be OK to use?
 
SuperRoo said:
Well, the jeep passed her roadworthiness yesterday, so she's good for another year.:cheers:

Thursday evening I checked the fuse and it was fine. After remembering having read numerous posts of fuses which "looked" OK, but apparently weren't, I decided to change the fuse - I received 4.71v at the TPS. Not quite 5.0v, but enough to get me sorted for the time being...any suggestions on where the rest of the voltage has gone to?

Couldn't find dielectric grease anywhere, the electronics shop sold me "silicon grease", as when he typed in dielectric on his computer, silicon came up. The tube says - "high electrical insulation, waterproofs/repels moisture, high temperature resistance; ...smooth, non-melting for high surface resistivity & excellent resistance to tracking & arcing".
So would this be OK to use?
Click to expand...

Sounds like the stuff to me.
 
Yes, it will work.
 
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