1994 Cadillac EL Dorado

Try pressing off and warmer on the climate panel with the key on, and see if it will enter diagnostics. If it does, record any codes or messages that it may display. When the lights on warning chime is going off, is that when the key is off, and the manual headlight stalk is pulled? Does the info center display headlamps suggested when the twilight sentinel is all the way off, the car is on, and it is low light?

There was also some info that I requested on the light issue. The info on your codes is as follows.

Code I052 indicates that the keep alive - or "long term" - memory in the IPC has been reset. It is a normal occurrence whenever power or ground is removed from the IPC, such as anytime the battery has been disconnected and reconnected. When the code is set, IPC memory is reset to initial values; the climate control will revert to 75 set temp, "Auto" mode and "Auto" fan speed. Code I052 will disable all other codes.

If code I052 sets without a battery disconnect, ensure good terminal contacts at power feed pins "A1" and "C12", and grounds at pins "A5" and "C16".

A011
CIRCUIT DESCRIPTION
The Hi Side Temperature sensor is a thermistor that controls a signal voltage to the ACP. The ACP applies a voltage on CKT 732 to the sensor. When the sensor is cold its resistance is high, therefore the ACP will see a high signal voltage at pin "D14." As the sensor warms, its resistance becomes less and the signal voltage is pulled low through the sensor ground, CKT 407. This signal voltage will vary between 5V (open circuit) and 0V (short circuit).

TEST CONDITION(S)

Ignition "ON."
Code A010 not set.
Temperature greater than 30 °E
FAILURE CONDITION(S)
The signal voltages indicates less than -18 °C (open circuit) or greater than 179 °C (short circuit) calibrated.

ACTION TAKEN

HI Coolant Fan operation when A/C compressor operation possible.

The r061 and r062 are for airbag lamp driver faults, the fact that they are current, does the airbag lamp illuminate?

The P052 and P109 are PCM memory reset indicators, and do not necessarily indicate a fault unless the set without battery disconnect.

The S0XX codes are all relevant to suspension system, and have no particular relevance to your symptom.

You could have seperate issues with the myriad of symptoms you have. The fuel reading, and battery voltage are direct inputs to the cluster. Check that fuse A11(trunk fuse panel), and A3(engine compartment) have power across them and are good. A11 powers the fuel level sender, and A3 the battery input to the cluster.

Among other things, and I suspect you may find one or both of these fuses open, fuse A3 also supplies power to the IPC, headlight/twilight sentinel, SIR module(derm), and the low pressure A/C switch, although your code is for hi pressure sw(or so the info says, and info can be incorrect). Fuse A11 supplies several things as well, but not as much for relevance. Give this stuff a check, and let me know the outcome.

The fuses are good, but do you have power across them? I would not suggest a PCM at this point, your symptoms do not point to it, and you have little cause other than memory reset codes that were stored in history, and could have been caused by a low voltage condition. You say horn blows when lights are on, do you mean the chime, same chime that sounds with a key in the ignition/door open, and is this with key on/running. Does your airbag light come on, and do you still have the R061 and 62 current?

A11 in the TRUNK fuse panel receives power from the ignition switch, as well as 7 fuse in the engine compartment fuse panel(A1, 3, 5, 7, 9, 11, and 13). If you have no power on A11, is there power on the others? This could suggest a problem with the ignition switch, if there is no power on any of the above. There could also be a circuit problem(splice/connection), if there is power on some but not others. If there is truly no power on or across A11, these other fuses need to be check and the determination could be made from there.

When it reads PCM, that is the signal that all codes have been displayed, and the system is ready to process the next request. If you use your fan button and scroll down it will show all the modules with XXX, and if you fan up, you will open the possibilities of options for that module like data, inputs, outputs, overrides, and clear codes. I am trying to determine if you have a common fault, or several different faults. I suppose next what you would have to do, is access the instrument panel cluster, or at least the connectors, so you can start checking if battery voltage(for charge info) is getting to it. The park brake release inoperative is not likely a symptom of anything other than a failed vacuum release motor.

I did a little research, and the most that I can come up with is a possible cluster fault, or a possible UART data line fault. You did not make mention on the airbag light, the request for that is an input to the IPC. The park brake switch is an input to the IPC, from there I believe a buss message is sent to the A/C programmer, although I could not find information to support this, it could also be a mechanical vacuum switch on the shifter. The fuel level, which at first you mentioned was inoperative, but have not mentioned, is an input to the cluster. The battery charge is an input to the IPC as well. What defines A/C not working, is it that the blower does not work, the compressor does not come on when requested, the display is blank or shows dashes, or is non functional? A/C information from the cluster is via data line to the programmer. As far as the door locks, I have yet to find any operational, or electrical diagrams that explain who sends the request to lock the doors, it too could be a data line message sent to perhaps the keyless entry module. So you have some common denominators, but I am not saying it is a faulty IPC. On the lights/chime, etc. There is a lights on input to the chime module from the headlamp switch, the IPC can also control the chime module. If it only occurs with the headlamps, it would tell me that the chime module may not be getting ignition power, there pops in that circuit from engine compartment fuse A3. That is where I am in suspicion. You say the fuses have power, and are good, what method of checking have we employed? The reason I ask, is that fuse A3, or the circuits from it, are to me a smoking gun, and this is why. Fuse A3 supplies key on(ign) power to: The low pressure a/c switch(it can prohibit compressor operation), the chime module(ign power only, still has B+ so in theory still powered, i.E. False key off lights on condition), the airbag module(airbag light), two ignition feeds to cluster(possible fuel gauge/charge), through prndl switch to keyless module(door locks), the headlight switch, on the same circuit as the chime module. It just has all the ingredients to be causing the issue. Knowing that, you are going to have to do some teardown, and electrical checks of those circuits to isolate this any further. Tell me this in you next reply, do you have backup lamps, and cornering lamps. The backup lamps are self explanatory, cornering lamps if you are not familiar, are the clear bulbs in front, that illuminate when a respective turn signal is activated. There are some who have not known of the cornering lamps, and to avoid a return post that reads, 'what are cornering lamps?', I thought I would include that info for reference.

Are you committed to doing some teardown and electrical checks, because that is the next step? What you are going to be faced with is component location, connector identification, and electrical checks. If done improperly, it can lead to incorrect results, consequential issues(terminal damage, etc.), And above all, frustration. Chances are you are dealing with a circuit problem, and you need to eliminate the possibilities. Another possibility to complicate matters, is I don't have factory information for your vehicle. I have basic info provided through second party online sites. Ther may be info that I can't obtain like locations, physical ID of connectors and terminal types, etc.

Good Job, and glad to hear of a resolve. You provided a good description of the symptoms, and that plays a large part in working toward a diagnosis. Especially with a vehicle sight-unseen.