2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Specific repair issues for Ford cars & FWD vans
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CalRewireMatt
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2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by CalRewireMatt »

Firstly, Ive been a Mitchell user for years and didnt know there was a forum of mechanics to help each other, this is a godsend for help with hard issues.

Speaking of tough issues, I have a 2005 Lincoln Town Car in the shop with an issue relating to the cruise control. Cruise wont turn on and going through the diagnostics the ohm reading were off a little so I bought a new cruise switch thinking if the resistance was slightly out of range could be enough to go inop. Changed the switch same issue. Scanner (Ease) shows cruise switch reading incorrectly ie: Resume = - - -, + = resume ect. Thinking thats odd I took a potentiometer and jumpered it into the cruise switch connector. I ran it through its sweep and found that resistance of over 500 ohms less would read on the scanner. (dont have exact resistance on hand but for example) 57 ohms on pot would set the coast on the scanner which should take 550-650 to set.

I did continuity and resitance tests between switch and PCM and everything fell in line. Figured it to be a PCM. I obtained a used PCM to try. This is where my issue is getting tricky.

I have an Ease J tool reprogrammer that in the past has been successful at reprogramming Ford PCM and BCM ect. Going through the Motorcraft program (which really sucks if youve had experience with it) every time I attempt to reprogram it I am asked to turn the ignition on and then off three times or so then errors out that it can reprogram it.

Im thinking that since the PCM is used I may need to do a PATS learn of a blank key first and then reprogram but I dont want to buy a key for it not to work.

Hoping that someone may have some advise about what may be going on. It gave an error code with a bunch of numbers and letters like 08x-??? but didnt write it down just huffed off after spending 3 hours trying to program a damn PCM and getting the same issue.

Customer is a good friend so Im not under the gun but I wanna get it fixed and I really think its the PCM. Maybe this is a common issue I dont know about and maybe theres a fix that isnt in the computer. Im tearing my hair out on this as it just doesnt work when it should take a few minutes.
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by timbre4 »

Welcome to the forum! I'm sure some of the regulars will be along shortly to comment on your issue. :wink:
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by Stewart Levy »

Most of the time with this isuue we find the clock spring to be the problem!
If they don't know how can they fix it!
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by ricmorin »

I doubt it's a PATS problem. An incorrectly coded key will still turn the ignition on, just not start it. I'd recheck my testing and look at the clockspring as a possible culprit. We too have replaced these for cruise issues. I never tried reprogramming a used Ford PCM. Always went new. I've had issues reprogramming other used modules though. I try to stay away from used on modules but I understand where you're coming from.
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by Tim Martin »

I have replace more than enough clocksprings due to cruise not working. Not saying that is the issue here but from what you are describing it would seem to be.
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by CalRewireMatt »

Ok fair enough on the clock spring.

Here is the issue with that part of the deal based on my tests. I ohmed both leads from the switch connector at the wheel to the PCM connector (pin 19 and 30 off the top of my head) and I had low resistance on both wires. Then I pinned on to those two pins and plugged the switch back in and the new switch is dead on for resistance through the loop. This was done with the pcm connector unplugged if youre wondering.

On the scanner the PCM always thinks the ON button is pressed. I cant get it to register off, -, + or resume in the correct posistions. Pressing + gets resume on the scanner and resume, - and off get dashes ---. To repeat what I said last night, I took a potentiometer and hooked it up in place of the switch and did a sweep. I was able to get all functions to read but the actual resistance at which the read on the scanner were biased low by ~500 ohms. Thats why I think it may be the PCM.

As far as the PATS, I figured without doing a replacement key rrelearn it would lock me out of doing any programming. A key is 26 bucks so its not horribly expensive but its 26 bucks Id like to skip if I can help it.

Tomorrow, just to be sure, Ill wire in the switch into the harness at the PCM directly to make sure there is no issues relating to the wiring. If it works there Ill replace the clockspring. If not I cant help but think its the PCM.

Thanks for the input, if theres any other ideas based on what Ive added or cleared up here lemme know. Thanks
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by Cory »

Ask your customer if they have two keys, if so have them bring the other one down, you do not need a blank key to reprogram, but you do need two keys. When going through the relearn process your programmer should find that the vin number does not match the other modules in the vehicle. When it finds this, it will ask you which vin number is correct, be sure you pick the right one or you will have other problems. BTW if your customer does not have two keys, then you are doing them a favor.
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by CalRewireMatt »

Update...

I did need to get a blank key and do a PATS learn for an additional key. New PCM works and car runs, cruise still has the same issue.

So I went onto verifying if the Clock spring was bad. I stripped back insulation on the blue/black and dk grn/orange leads at the PCM ( well about an inch from the connector) and clipped on two wires. Crimped on some terminals and slid them onto the pin of the cruise switch. Did a test again and same issue.

Im at a total loss now. I have NEVER, EVER replaced this many parts with zero correction. Sometimes Ive found multple issues that compounded a single one and an improvent is found after one part is fixed. This is disappointing to say the least. I pride myself on being able to verify the problem and with certainty recommend the correct repair first try.

I dont want to give up on this as everything can be fixed and Im usually the one that can do it but this is one that may just beat me.

So is there anything else that could be causing this that Im not seeing? Ive tested the cruise deactivation switch and that is working. Rear light module and ABS both register a brake input. Im afraid Ive locked myself into a single mode of thinking and have missed something else in the process.

Hope an :idea: pops up that gets me moving in the right direction. Thanks agin.
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by steven kiser »

are one of the safety interlocks malfunctioning? not in lincolns but i've seen after market remote start kills wired into the brake switch incorrectly. what was done prior to this issue.........
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by Cory »

Check to make sure ALL Brake lights are working, including third high mount light. Most of the time the cruise control needs to see the feedback from the bulb, and if it is not there, the cruise will not work.
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by ricmorin »

Lets start over. In test A2, there is a chart for resistance for each of the cruise switches. Can you tell us the results of that test? Move the steering wheel around a little while testing. Test at PCM connector disconnected.

As far as your pot. test, could the pot be off 500 ohms?
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by CalRewireMatt »

ricmorin wrote:Lets start over. In test A2, there is a chart for resistance for each of the cruise switches. Can you tell us the results of that test? Move the steering wheel around a little while testing. Test at PCM connector disconnected.

As far as your pot. test, could the pot be off 500 ohms?
I let him go, BUT if I can come up with something Ill have him come back to check it.

Test A2 was PERFECT with the second switch. I checked the switch out of the car which took me and some one pressing buttons while I held it in my lap. I was within a 1/100th an ohm at the PCM WITH IT UNPLUGGED as it was sitting in my lap. As a last resort I stripped back the wires at the PCM, attached jumper leads and with some terminals I had pressed them onto the pins of the switch. I still had the same issue. This counts out any issue with the Clock spring as I tested the switch after the it. Being so close to the the connector that rules out resistance issues in the wiring, bulkheads, ect. I tightened the terminals to rule out a loose connection. Im thinking there is another module involved if it is in fact hardware or software related.

In regards to my testing equipment, in the past Ive used pots to test certain gauges and figured this would be a good time to use one. What I did was sweep the pot and when I saw a parameter that wasnt showing up with the switch, I stopped and put my meter over the pot to see what it was at. As far as my meter is concerned Id notice it WAY before this as I use it all day long for multiple tests. A meter reading off that much wouldnt be able to properly do a continuity test when I touch the probes together. ( I also check it from time to time with a set of precision resistors to make sure the meter and my leads are all good as I had issues in the past with worn out leads that caused issues in the past). My leads at this time have minimal resistance and I polish the probes every month to make sure no corrosion is building up. Regardless 500 ohms is huge and would be noticable for me.

All the brake lights function as that was an early test. The two wire deactivation switch was removed from the brake pedal and checked for continuity, reinstalled and verified on the scanner.

According to the test,s I was able to proceed through the tests of the Rear Light Module as well as the ABS for the PIDs it calls on to test. There is always the possibily that a pid Im not looking at is the culprit. Thats what has me stuck right now.

I keep going back to the issue with the scanner showing incorrect data for the cruise switch.

Is there ANY reason the PID should read incorrectly due to an issue with another module or a component other than the switch itself that is screwed up? This is the last thing I can think of. Maybe theres an issue with something else that is keeping the cruise from functioning that my customer or I hasnt noticed? Say the ABS is problematic but not throwing a code but is keeping the cruis from working..

Some of these things are found by dumb luck but I hope theres a way to figure this out by logic..
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Re: 2005 Lincoln Town Car - Can't Reprogram PCM Cruise

Post by steven kiser »

Some of these things are found by dumb luck but I hope theres a way to figure this out by logic.. :lol: :lol: :lol:
never argue with a fool, they'll drag you down to their level and beat you with experience
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