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post #1 of 15 Old 08-28-2019, 10:01 AM Thread Starter
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so recently I made post which was helpfully responded to buy forum member NAJ, and my main concern was that my 1986 Chrysler Town and country has been in limp mode and one of the culprits based on the codes being tossed was the coolant temperature sensor. I wasn't able to back probe the existing coolant temperature sensor because I lack a voltmeter -- so I decided, the hell with it, I'm just going to replace it anyway.

so I got a part from the local AutoZone which came with the wiring harness and I reattached it restarted the computer by disconnecting the battery and turn the car over after reconnecting the battery and everything seems to be fine. (typically with the last coolant temperature sensor the radiator fan would come on automatically telling me the car was in limp mode.)

this morning I turn the car over again to double-check and the radiator fan kicked on and I was again receiving code 22 regarding the coolant temperature sensor voltage being out of whack.

I did notice that the replacement part I got had a slightly larger nipple than the pre-existing one. however when I reinstalled it - it bottomed out on snugly and there were no leaks.

I'm concerned that this slight difference in part might be the issue? or perhaps the part is fine and there's something else going on.

any input?

Edit: I bought the exact fitting CTS that I was originally going to purchase and respliced the old harness because I was worried it was not correct part. I'm still have limp mode issue.

Last edited by ChryslerTC1986; 08-29-2019 at 06:18 AM.
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post #2 of 15 Old 08-29-2019, 09:26 AM
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Re: Having limp mode issue replaced CTS -- didn't work

You will need to purchase a Digital Multi-Meter in order to diagnose and locate and repair the problem.

A fault code indicates the circuit that is setting the code, it does not tell you where the problem in the circuit lies.
Besides the sensor you could have a wiring or controller issue, it is those three components that make up the entire circuit.

Let me know when you get a meter and we will proceed with diagnostics on your Code 22.

I am "assuming" the Code 21 is gone since you did not mention it???

You do not need anything expensive, I use a $10.00 meter all the time, I have other meters in my toolbox at my Son's house which is 16 miles away but at home I use this, if you are only checking Volts/Ohms/Low Amperage it works as well as any meter out there.
https://www.dormanproducts.com/p-30559-85357.aspx

Here are some other inexpensive meters
https://www.walmart.com/ip/Hyper-Tou...i-Meter/876903

https://www.harborfreight.com/7-func...ter-63759.html

https://www.homedepot.com/p/Gardner-...-311/202867882

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post #3 of 15 Old 08-29-2019, 10:20 AM Thread Starter
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Quote:
Originally Posted by NAJ View Post
You will need to purchase a Digital Multi-Meter in order to diagnose and locate and repair the problem.

A fault code indicates the circuit that is setting the code, it does not tell you where the problem in the circuit lies.
Besides the sensor you could have a wiring or controller issue, it is those three components that make up the entire circuit.

Let me know when you get a meter and we will proceed with diagnostics on your Code 22.

I am "assuming" the Code 21 is gone since you did not mention it???

You do not need anything expensive, I use a $10.00 meter all the time, I have other meters in my toolbox at my Son's house which is 16 miles away but at home I use this, if you are only checking Volts/Ohms/Low Amperage it works as well as any meter out there.
https://www.dormanproducts.com/p-30559-85357.aspx

Here are some other inexpensive meters
https://www.walmart.com/ip/Hyper-Tou...i-Meter/876903

https://www.harborfreight.com/7-func...ter-63759.html

https://www.homedepot.com/p/Gardner-...-311/202867882
I just picked one up yesterday, it is most likely middle tier quality and seems to work real well. I used it to test a few things yesterday. I would be more than happy to run some more tests to figure out the overarching problem that I am facing. I'll be working on it today and checking the forum periodically. thanks again NAJ!


also, I haven't noticed a code 21 yet. I did however check the O2 sensor and it seems like the single wire had a compromise in the sheathing and noticed the wire exposed.
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post #4 of 15 Old 08-30-2019, 10:24 AM
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Re: Having limp mode issue replaced CTS -- didn't work

I am assuming you did clear the codes and the Code 22 and Power Loss Lamp returned.
If this is correct...
You need to start by backprobing the CTS connector with your Digital Voltmeter and reading the voltage, specific voltage = a specific temp, let the car run and watch the voltage/temp until the fan cycles on.
Starting with a Cold Engine...
1)With the key on/engine off is the voltage/temp reading accurate to ambient temp?
If Yes, start the car...
2)Does the voltage change with temperature?
3)Did the voltage reach the point where the fan should cycle on?

If you do not have backprobe pins you can use paper clips, just be sure the backprobe pin/paper clip is making a good connection with the terminals in the connector.
If you do use paper clips do not let the clips or leads from the meter touch each other or your readings will be incorrect.

Having limp mode issue replaced CTS -- didn't work-cts-voltage-chart-2.jpg

Having limp mode issue replaced CTS -- didn't work-backprobing-cts.jpg

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post #5 of 15 Old 08-30-2019, 04:09 PM Thread Starter
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it looks like when I test it for voltage as the engine temp increase so does the voltage.. how is that possible???

I also noticed that the black/blue wire is the only one which gives me continuity while the tan wire doesn't give me any. but I've checked the wire and I don't see any real damages to it. connectors seem fine. thoughts?
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post #6 of 15 Old 08-31-2019, 11:06 AM
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Re: Having limp mode issue replaced CTS -- didn't work

Lets not jump too far ahead, one step at a time.

What was your initial voltage reading on a cold engine with the key on/engine off?
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post #7 of 15 Old 09-01-2019, 05:56 PM Thread Starter
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Quote:
Originally Posted by NAJ View Post
Lets not jump too far ahead, one step at a time.

What was your initial voltage reading on a cold engine with the key on/engine off?
practically nothing.
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post #8 of 15 Old 09-02-2019, 09:46 AM
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Re: Having limp mode issue replaced CTS -- didn't work

There are two wires at the CTS...
1)Tan (TN)
This is the 5 volt signal the engine controller sends out to the sensor.
2)Black/Light Blue (BK/LB)
This is the signal ground/return.

1)Disconnect the CTS connector, connect the black lead of the meter to a good ground.
Turn the key to the On position and using your meter touch the + probe to the TN wire terminal.
(Do not push the probe into the terminal as this will spread/damage the terminal, just touch it).
You should be reading 5 volts (4.90 is acceptable)
If you reading 5 volts move to step 2.
If you are not reading 5 volts the next step is to check for 5 volts at the engine controller connector.
The 5 volt signal comes from the Logic Module Black (TBI, Blue on Turbo) Connector Cavity #23.
(The LM is located behind the R/S (passenger) kick panel.
Again check for 5 volts by backprobing the LM BK Connector Cavity #23.
Is there 5 volts present?
If Yes then you have an open wire between the LM and CTS.
If no, verify there is no damage to the connector/terminal.
(It is very common for these terminals to become corroded from moisture entering the inside of the vehicle, usually from the antenna mounting).

2)Disconnect the CTS connector and the LM White (TBI, Red on turbo) Connector.
Set your Meter to the 200 Ohm's scale (Ω).
(Ohms are a measurement of resistance in a wire/circuit)
In this case we are going to check to see if the wire from the LM to CTS has continuity (a complete circuit) or if it is open (broken).
Touch your meter probes to the terminal on the BK/LB wire at the CTS and the other to the terminal at Cavity #25 of the LM WT connector.
You should be reading less than 5 ohms.
(An open circuit (infinity) will be displayed by an OL (out of limits) or whatever your meter reads when set to ohms and the two probes are not touching, when you touch the two probes together the meter should read "0".)
OL may also be displayed if the resistance in the circuit is higher than what your meter is set to, IE...
You are testing an ignition wire that will have approx 3000 (3K) ohms per foot but your meter is set to a 2000 (2K) scale.
In this case checking a wire with no load device in the circuit (light bulb, relay, solenoid, sensor) we want less than 5 ohms resistance.
Do you have continuity(does the meter show an ohm reading which would indicate a completed circuit) and if yes is it under 5 ohms.
If you do not have continuity then we need to locate the open in the ground/signal return wire.
Again, corroded, damaged terminals in the connector or LM could be the cause.

If you have corroded terminals first use a spray battery cleaner to neutralize the corrosion and clean the terminals using a soft toothbrush or Q-Tips, be gentle with the brush.
Once the majority of the corrosion is clean on the connector and LM use an electrical contact cleaner on both the connector and LM.
Spray both then connect/reconnect the connector a few times and repeat, this will help to remove corrosion/oxidation from the inside of the terminals.

Now that you are thoroughly confused...
Enjoy your Labor Day and I will be back on tomorrow.

Having limp mode issue replaced CTS -- didn't work-85-87-lm-tbi-black.jpg

Having limp mode issue replaced CTS -- didn't work-85-87-lm-tbi-white.jpg

Having limp mode issue replaced CTS -- didn't work-cts-1.jpg

Having limp mode issue replaced CTS -- didn't work-cts-2.jpg

Having limp mode issue replaced CTS -- didn't work-cts-3.jpg

Having limp mode issue replaced CTS -- didn't work-cts-4.jpg

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post #9 of 15 Old 09-03-2019, 08:51 AM Thread Starter
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I just got into the LM and before I went to head back probing anything I've disconnected the black connector and found a decent amount of corrosion on some of the terminals and I'm assuming that that is the main cause of my situation. I'm still going to back probe to see if I see anything but I would be surprised if I do right now I'm just going to focus on cleaning this up.

just checked voltage at #23 to a good ground. I got 2.84 volts. assuming the corrosion has something to do with it.

also I tested #25 to the bk/lb for ohms and I received a beep less than 5 but not OL.

I am going to start cleaning the
black connector.

thank you so much for providing me with such detailed explanation of the problem you are seriously a god!!! he has spoken!!?

do you suggest I treat the connectors with dielectric grease? after I clean them up?
any way to prevent future corrosion?

also someone on another forum said that I should not wrap the threads for the CTS in Teflon because the metal acts as a ground. I don't think this is necessarily true. thoughts?

I owe you a beer good sir
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post #10 of 15 Old 09-03-2019, 09:07 AM
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Re: Having limp mode issue replaced CTS -- didn't work

Looks to me like you found the culprit, common problem.
Clean both the connectors and LM terminals and let me know what happens.

If you do not have access to a compressor you may want to also purchase a can(s) of compressed air to blow everything out while you are cleaning.
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post #11 of 15 Old 09-03-2019, 10:26 AM Thread Starter
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there was a moment of excitement and hesitation as I put the key in the ignition and waited to turn it on considering whether or not how did my hopes up make me disappointed or not when I turn the key....

big smile came across my face when I noticed the fan didn't come on automatically I turn the car over and things seemed to be perfectly fine, checked the codes, code 22 disappeared... hallelujah!!!

now I have to bring it into the shop to get the CV joint replaced. I'll let you know if any other developments occur with the CTS.

I don't think you understand how much I really appreciate you helping me!

never leave the forums!

edit: so attached is a photo of the temperature gauge. I recall in the past that the temperature was always slightly below middle before the fan kicked on. I'm not sure why this might be. could it be the gauge?
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Last edited by ChryslerTC1986; 09-03-2019 at 03:38 PM.
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post #12 of 15 Old 09-04-2019, 09:20 AM
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Re: Having limp mode issue replaced CTS -- didn't work

Very happy to hear that this was an easy fix and cleaning the corrosion did the trick.

The factory gauges are not accurate, as long as it reads somewhere in between Cold and Hot and is not pegged either way, that is all the factory gauge is intended for.

Since I have owned my car (12/89) the gauge will only read 1/4 the way up in winter when the fan cycles on while it will reach the 3/4 mark in the summer when the fan cycles on, in both cases the coolant temp is the same and where it should be when the fan cycles on.

The gauge does not read accurately due to where the sending unit is located.

The CTS only provides coolant temp to the engine controller, the engine controller uses this info for fuel/spark advance parameters and to cycle the cooling fan on/off.
The gauge uses a separate sending unit located in the cylinder head above the oil filter that works solely on resistance in the circuit.

Chrysler actually issued a TSB (Technical Service Bulletin) concerning temp gauge fluctuation in cold weather that this was normal and why so techs were not chasing their tails looking for a problem that did not exist.

If you want to know the actual temp that your fan cycles on and off then backprobe the CTS and watch the voltage and compare to the voltage to temp chart.

If you run into any other problems, have any concerns/questions or need/want info Please feel free to ask.
My PM box is always open.

Chrysler Temp Gauge TSB
Having limp mode issue replaced CTS -- didn't work-5-cooling-system-tsb.jpg

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post #13 of 15 Old 09-05-2019, 03:10 PM Thread Starter
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wow okay that's very interesting.. im impressed with your wealth of knowledge about these machines.. and I appreciate the accompanying literature!

one thing I'll mention is that even though the weather has been staying around 70F outside the temp gauge stays barely above the tick marks.. it just seems like that is low..

new radiator
new Tstat
new coolant
obviously we know new CTS

just seems odd...

I'll run a back probe tomorrow to figure what the temperature is inside..
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post #14 of 15 Old 09-05-2019, 06:08 PM
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Re: Having limp mode issue replaced CTS -- didn't work

If the level is staying where you pictured it a couple posts up that's fine. Right where it should be while the car is moving. Now when it sits it'll rise to 1/2 maybe close to 3/4's and then the t-stat will open and it'll drop back down. Either leave the CTS sensor back probed or by an OTC scanner and see what the ECU is seeing for engine temp as well as a # of other things for about $100 maybe less on Ebay.
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post #15 of 15 Old 09-05-2019, 08:27 PM Thread Starter
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Quote:
Originally Posted by GLHNSLHT2 View Post
If the level is staying where you pictured it a couple posts up that's fine. Right where it should be while the car is moving. Now when it sits it'll rise to 1/2 maybe close to 3/4's and then the t-stat will open and it'll drop back down. Either leave the CTS sensor back probed or by an OTC scanner and see what the ECU is seeing for engine temp as well as a # of other things for about $100 maybe less on Ebay.
the tstat gauge was reading the indicated amount in the picture when the car wasn't moving. when it is moving it drops down to about half what is shown in the picture. which is a bit concerning. hardly to do I ever see it at halfway or above.

I'm going to back probe it to see exactly what temperature is being tossed out through the voltage being read.

I purchase an OTC scanner from eBay but the seller didn't realize it wasn't in their inventory was tossed out so they bag it and gave me a refund. I decided to nix the whole bag because the issues I was having resolve themselves through to previous troubleshooting from NAJ earlier in the thread.at some point down the line I will buy an OTC scanner because it definitely seems to be a good investment. they seem to be kind of expensive especially since most people tend to sell incomplete sets either you get the scanner no cartridges or you get the cartridges with the hardware and no scanner.
some of the listings were as much as 150 bucks or higher!!!
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