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1996 eldorado
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Discussion Starter #1
Hi all I'm new to this and I'm also new to Cadillac ownership. I bought a very good 1996 Eldorado Florida car no rust and only
130000 kms.I like the car very much , I really like the lines. I am however becoming disenchanted rapidly. I've owned the
car for about 5 months and already have had to replace alt. a/c compressor among other things then the prindl started
flashing and anti-theft message came up, I tried a veriety of things to no avail then took it to a small shop that had it for
about a month then took it to the dealership for proper diag. they said all things pointed to the pcm, replaced it and all was
well for about 2 wks when all of the sudden the prindl started to flash and anti theft message appeared as well as my a/c
control unit when black. Car started and ran and for some reason I turned on my headlights by pulling out the knob and low
and behold the prindl stopped flashing and message disappeared and the a/c control unit came back to life, so every time I
turn the lights off everything gose nuts and back to normal with headlights turned on manually. Has anyone heard of this
and my question is, is the headlight switch assembly tied into the anti-theft some how. Any assistance would be gratefull,
I'd really like to like my car again and be able to trust it
THANKS

MIKE
 

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Super Moderator
2010 DTS
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87,551 Posts
Re: prindl flashing

:welcome:

What's a "prindl"?

A good place to start is by pulling the DTC's. Post them AND their definitions. See the DTC Sticky at the top of the forum page if you need help. Keep in mind that '96 was the transition year from OBDI to OBDII so any codes definitions you don't find in the OBDII link will be in the OBDI link.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
PRNDL: Park, Reverse, Neutral, Drive, Low. The shift indicator.

Some people believe it's a word (prindl).
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Re: prindl flashing

NO, is not tied into it, but may share a common ground!
There are 2 reasons the PRND321 will flash:
1) PRND321 flashing on IPC while the shifter is NOT in Park (you just shifted into a gear) it means the shifter is in a intermediary position between gears.
2) PRND321 flashing while the shifter is in park (say you never touched it) it means IPC has no data communication with the rest of the car modules. It will also post every single conceivable message on the display plus most of the warning lights will be on (not the case for 1) as shown in this picture of a IPC powered on a bench (no data communication).


You have to pay attention and tell which of the 2 situations apply to you.
Also you need to pull your codes. CLICK HERE TO LEARN HOW (no need of a scanner, the car has one integrated).

Post the codes AND the definitions. Pay special attention to the IPC "U" codes. The PCM was changed for no reason, will not cause the issue you mentioned.
Your car being a '96 officially is OBDII, unfortunately is not fully OBDII, you may find yourself using OBDI code definitions as well. I HATE '96 cars, are so difficult to diagnose with the confusing codes they have.


Off course a miss aligned cable may trigger situation 1 even with the shifter (in what you believe to be) P, so again pay attention to the details.
 

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1996 eldorado
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7 Posts
Discussion Starter #5
Re: prindl flashing

Ck'd it out again the only light on in the IPC is the flashing PRINDL and or course the A/C control head is dead and as before as
soon as I turn on my headlights the IPC returns to normal and the A/C control comes to life I checked for codes and there are
many but they are all history codes. Then I turn off the headlights and prindl flashes and a/c control gose dead??????????????
Car starts fine and runs fine, when prindl flashing get anti-theft message I'm stymied.
THANKS
MIKE
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Re: prindl flashing

You have an INTERMITTENT issue, it just happen to be that when you check the codes the issue is not current.
Unlike what you may be told, the history codes are EQUALY important with the current codes. The problems don't fix by themselves.
Post all the codes here along with their definition for diagnosis.
 

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98 eldo/KD54 w/N37,T96,QA1,D55,DS3,U1Z. U3R next
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2,125 Posts
Re: prindl flashing

Ironically, this came up in conversation this evening on an eldorado.

Make sure the vehicle is in gear completely. The shifter should feel "seated" when you put it in any particular gear. If it is a bit out of gear or "off seat" I was told the PRND321 will flash.

I would also check your range selector switch mounted on your transmission for proper adjustment along with the shifter cable.
 

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1996 eldorado
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7 Posts
Discussion Starter #8
Re: prindl flashing

I will ck the the gearshift selector and cable but that dose,t address the issue with the a/c control head gong dark and coming back to life when headlights
turned on
thanks
mike
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Re: prindl flashing

Still don't see the codes, you are just jumping left or right with no reason. The codes tell you which way to jump and how far.
If I would have to guess I would say you have a ground issue rather than a cable adjustment issue but I am just speculating. I clearly told you to pay attention if is 1 or 2.
 

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1996 eldorado
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7 Posts
Discussion Starter #10
Re: prindl flashing

pulled codes they are as follows PC1602,1604,1605,1610,1611,1626,,,,,,,IP1552,1910,2016,2064,2152,2750,,,,,,TC0072,,,,,PZ2476,2016,2096
5152,2153,2255,,,,,,,,IR2255,2064,2096 CHECKED 2 DAYS AGO ALL WERE HISTORY CODES EXCEPT PC1626 AND PZ2255
CHECKED AGAIN TODAY AND ALL ARE HISTORY CODES. THE SITUATION IS NUMBER 1 PRNDL FLASHING NO OTHER LIGHTS AND AGAIN EVERYTHING GOSE
NORMAL WHEN HEADLIGHT SWITCH PULLED OUT

THANKS
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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Codes are meaningless without definitions. Go back to the sticky, and click on the link to OBD II code definitions.

That many random history codes often means there's a low voltage issue. What's your voltage with the engine OFF? Preferably after being off for 30 minutes or more.
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Re: prindl flashing

I can't find all the code (sorry not enough time) as I mentioned your car is OBDII (almost) so is a bit of a search to figure out what are the codes (BODI or OBDII). But form what I see you are missing the voltage to the IPC, one code is about the keep alive memory (means IPC lost power), one is about terminal L on the alternator, one is key validation.
A bad ground, a low battery voltage or a bad connection at the IPC connector could cause all these.
Please come back with all the code definitions I don't care what's current and what's history, in your case are EQUALY important.
 

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1996 eldorado
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7 Posts
Discussion Starter #13
Re: prindl flashing

here is an update, I've been thinking about all those codes and came to the conclusion that most of the codes are
probably related to the problem I had with the anti-theft issue which caused no start ,dead battery, ipc removal and replace
and finally pcm replacement. So I made a list of the codes and then proceeded to clear them, driven the car for a day and the codes that reappear
are pc 1605 hvac loss of serial data and pz 2255. The problem that still exists is when I start the car the a/c control head is dead
as soon as I put the car into gear the prndl flashes and as soon as I turn on the headlights the prndl stops flashing and goes back to normal
and the a/c control; head comes to life. I'd like to thank everyone for their input
mike
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Re: prindl flashing

DON'T replace IPC and PZM, 99% is a wiring issue not a module issue.
Sure is easy to replace a module, just unhook the connectors, and this is why people go for it as not most know how to check wires.

Replacing the IPC requires the IPC VIN RPOs and SIR registries to be programmed matching your car. The mileage must also be programmed (this is legal matter).
Replacing the IPC requires reflashing it.

When either one of these 2 modules is replaced the password relearn procedure must be performed (takes 30 minutes or 10 having a TechII).

Then you have to worry about VAT, there are 10 VAT values and you have 1 in 10 chances the replacement IPC VAT will match the original. This means you need to get new ignition keys with matching VAT.

The fact you have Theftlock issues YET AGAIN suggest me you have WIRING issues. I would suspect maybe water damages (corrosion) in the IPC connector.
Again I have to point again to provide the definition for the codes, I only try to help you so far, at some point I will give up.
 

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1996 eldorado
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Discussion Starter #15
Re: prindl flashing

Hi here are the initial codes and definitions there are many
PC 1602.....knock sensor modual performance
1604....loss of IPC serial data
1605....loss of HVAC serial data
1610....loss of PZM serial data
1611 loss of CVRTD serial data
1626....theft fuek enable signal not recieved

IP1552....loss of PZM keep alive
1910....generator l terminal open
2016....loss of serial communication PCM
2064....loss of PZM serial data
2152....loss of serial communication HVAC programmer
2750....pass key 2 data communication failure

TC0072....IPC serial data line fault

PZ2476....park lamp output fault
2016....loss of serial communication PCM
2096....loss of IPC serial data
2152....loss of serial communication HVAC programmer
2153....loss of serial communication CPP
2255....generic loss of serial data id unknown

IR2255....generic loss of serial data id unknown
2064....generic loss PZM serial data
2096....generic loss serial communication IPC

those were the initial codes set I have cleared those codes and driven the car for almost a week
and the code thar have returned are as follows

PC1605....loss of HVAC serial data

IP2152....loss of serial communication HVAC
2016....loss of serial communication PCM
2750....pass key 2 data communication failure

PZ2255....generic loss of serial data id unknown
2152....loss of serial communication HVAC programer

these are the codes that reoccured I must reiterate that the car runs and drives fine the A/C control head dead and PRNDL flashing
with headlights off then ok with headlights on has me stumped

thanks
MIKE
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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Re: prindl flashing

Based on the codes I would say:
1. Low battery voltage
PC 1602.....Knock sensor modual performance
IP1552....loss of PZM keep alive
1910....generator l terminal open

2. Data line communication issues (a faulty module my pull the line to GND or to battery voltage, or corroded contacts)
All the data related codes. Since literally all modules are reporting the data line issue is not related with the IPC only, the IPC is the one you see acting because of the flashing lights but all modules are affected.

3. Missing ground (or positive voltage).
This is what could fool the IPC to see the L terminal issue, this could cause the PCM to see an issue with the knock sensor (if you crank the car with a weak battery EVERY time will post the Knock sensor code). A high resistance to ground or battery voltage is the same as a weak battery.
The fact that your issue is fixed with the headlamps on it means you get backed that fixes your issue.

I am 80% sure the issue is in the wiring somewhere between a ground and a fuse (corrosion, high contact resistance).

My advice is to clean every single maxifuse, fuse and relay contacts in the engine bay (to be found as indicated in the picture bellow).

Also clean all engine compartment grounds and the one near the parking brake pedal (underneath the plastic panel).
Obviously start with the 2 most important ground cables (the ones for the battery).

How to clean, just use ~200 grit sand paper, disconnect one by one a fuse/relay or ground and sand the contacts to shiny finish.
 

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2001 SLS, 2004 GMC 2500 DMax, 86 C10
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Re: prindl flashing

I don't have a lot of time to post right now or read this thread but Jake says to check the ground wire that comes off the exhaust stud by the coolant temp sensor. The rear of the RH cylinder head, drivers side. There should be 2-3 black ground wires attatched to that stud.
 

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1996 eldorado
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7 Posts
Discussion Starter #18
Re: prindl flashing

Hi
I havn't yet done what you suggested but I will just wanted to give an update. I have not had a problem in the last week or so
of driving. It seems to me that the issues are temp. related below 0 degrees problem starts above 0 degrees no issues I will do what you suggest
and keep you informed. just wanted you to know. I appreciate all your help.
Thanks
Mike
 
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