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1996 FWB coach
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9 Posts
Discussion Starter #1
About a month ago, I bought this car. It needed work, and I have done all the mechanical work, now I'm down to the system failures. Pass key code failure that I have been removing the 2 ignition fuses to reset to work. My car alarm has been disabled in the codes system, and I need to see how to check the codes for overheating issues. Just changed thermostat, and cant tell, coolant light stays on. Any advice on how to do this? I looked at the coolant thread, but it doesnt say how to access the system. Please help!!!
 

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1996 Fleetwood hearse
1996 Cadillac Fleetwood Superior Coach Hearse Conversion
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139 Posts
You access the system via the air conditioner controls. It is much easier to just get a code reader and plug up to the OBDII port under the dash. It is a lot easier than navigating the A/C controls. Your key's resistor could simply be bad with the pass key fail but you really need the codes. It is suggested you install a digital or mechanical temperature gauge on the driver's side head (there is a spot between plugs 2 and 3 I believe) and that will give you a better view of the engine temps. I'm going to point you to this thread as it is where I started with my 96 Fleetwood Superior Coach: How To Pull Codes (DTC's)
 
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1996 Fleetwood hearse
1996 Cadillac Fleetwood Superior Coach Hearse Conversion
Joined
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139 Posts
SimplyDarkness, you should join this page. Hearse's
 

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Super Moderator
2014 ELR
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10,159 Posts
LOW coolant light or HOT coolant light? Take us a pic, please. Or, show us the symbol that matches on google images.
 

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1996 FWB coach
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9 Posts
Discussion Starter #5
LOW coolant light or HOT coolant light? Take us a pic, please. Or, show us the symbol that matches on google images.
Low coolant light. Added DeX-cool, and it wouldn't suck it down. So I figure the thermostat was stuck and replaced it. Now I realized no temp gauge and just wanna make sure before I start driving it 30 miles to work that it's not overheating. 😊👍
 

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Super Moderator
2014 ELR
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10,159 Posts
Low coolant light caused by sticky float is NOTORIOUSLY is very very common on these cars. Here's how to fix it.
  • car on, idling
  • cap off
  • slightly overfill reservoir (above the line, look on the side)
  • with the side of your fist, or a rubber mallet, hit the side of the reservoir. HARD (with fist) a few times. Go look inside, light is probably off.
 

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96 FWB
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1,286 Posts
Be mindful going after the front side. I've got a crack on my black one bought new, and in exactly the same spot on my white one. I've heard others report the same thing:


Another cause of low light is of course low level, and it's programmed to take several drive cycles to cancel it.
 

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1996 FWB coach
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9 Posts
Discussion Starter #8
Low coolant light caused by sticky float is NOTORIOUSLY is very very common on these cars. Here's how to fix it.
  • car on, idling
  • cap off
  • slightly overfill reservoir (above the line, look on the side)
  • with the side of your fist, or a rubber mallet, hit the side of the reservoir. HARD (with fist) a few times. Go look inside, light is probably off.
I dont care that the light is on, I want to make sure its cycling fluid and cooling. I drive a ways to work, and dont want to overheat it on my way to work.
 

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96 FWB
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1,286 Posts
....... I need to see how to check the codes for overheating issues. ....... I looked at the coolant thread, but it doesnt say how to access the system. Please help!!!
The thing on the WP is usually referred to as 'sensor' and the idiot light comes from the 'sender' on the PS head. You can monitor and compare between the two readings as you drive -

Instructions for putting ACC in diagnostic mode -
  • turn ignition to ON position (or start vehicle)
  • press and hold the "temp up" and "OFF" buttons at the same time until the unit does a full segment check.
  • Release the buttons.
  • Display should read -00... you are now in diagnostic mode
  • Using the fan up/down buttons, select desired function from above
  • press the "middle" Button. It should be in the top right corner on the CC.
  • To Exit the trouble code area, and go back to the -00 display, hit the "Middle" button again.

You will see -00. You can change the funtion(it will say -01, -02, etc) with the fan up, and down buttons. Here is a list of what all the -00 numbers mean.

Diagnostic Pointers and Parameters
No. Description Range Default Value Units

-00 PCM System Diagnostic Trouble Codes ...............................................
-01 CCM System Diagnostic Trouble Codes ...............................................
-02 ACAC (HVAC) System Diagnostic Trouble Codes .......................................
-03 SIRSystem Diagnostic Trouble Codes ................................................
-04 ABS/TC System Diagnostic Trouble Codes ............................................
-05 Program number .......................... 0-255 ....... n/a ............. Counts
-06 Engine RPM
-07 Command Blower Motor Speed .............. 0-128 ....... n/a ............. Counts
-08 Coolant Temp (°F) - Reading taken at Cylinder head sensor, typically 20* cooler than the -24 reading
-14 Vehicle speed ........................... 0-199 ....... n/a ................ MPH
-15 HVAC Learn Mode (Temp Cal) .............. -5 to +5 F .. 0 F ............ Degrees
-18 Sun Load Sensor ......................... 0-255 ....... n/a ............. Counts
-20 Current Temperature Valve Position ...... 0-255 ....... 240 ............. Counts
-22 Temperature Valve Position (Full Cold) .. 180-250 ..... 180 ............. Counts
-23 Temperature Valve Position (Full Hot) ... 5-60 ........ 60 .............. Counts
-24 Coolant Temp (°C) - Reading taken at the Water Pump sensor, This is what the PCM uses to control the fans. Engine Coolant Temperature .............. -40 to 151 .. n/a ............ Celsius
 

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1996 Fleetwood hearse
1996 Cadillac Fleetwood Superior Coach Hearse Conversion
Joined
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139 Posts
Invest in a bluetooth OBD2 Reader that connects to your phone. There are several apps out there, some free, some paid but are really helpful for monitoring and troubleshooting. I use OBD Fusion and Torque. Fusion has a paid add on which I purchased for another vehicle but I didn't find necessary for the Caddy.
 
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Registered
68 DVC, 96 FLTWD Brgm, 11 CTS Premium (two)
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1,667 Posts
The diag mode on the AC pointer 24 is what I always use to check the coolant temps.
 

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1996 FWB coach
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9 Posts
Discussion Starter #14
I found a O2 sensor that wasnt plugged in and melted from sitting on the catalytic converter. Got it ordered, comes this Friday. How do you clear the codes through the a/c so I can see if anything else pops up? And how do you turn the alarm system back on? The guy who owned it before me turned it off. I have to do everything by key, even the kiosk doesnt work. Thanks!!!!!
 

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1996 Fleetwood hearse
1996 Cadillac Fleetwood Superior Coach Hearse Conversion
Joined
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139 Posts
I found a O2 sensor that wasnt plugged in and melted from sitting on the catalytic converter. Got it ordered, comes this Friday. How do you clear the codes through the a/c so I can see if anything else pops up? And how do you turn the alarm system back on? The guy who owned it before me turned it off. I have to do everything by key, even the kiosk doesnt work. Thanks!!!!!
Check out the section on keyless entry and security.

 

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1996 Fleetwood hearse
1996 Cadillac Fleetwood Superior Coach Hearse Conversion
Joined
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139 Posts
Thanks, now I cant find where the sensor plugs to. Its passenger upstream o2 sensor. I've looked for half an hour. ..
Look for a connector hanging down with some foil type wrap on it. It is a tight fit to get your hand up in there but it should be hanging down near the oil pan and above the cat. I've changed all 4 and both cats.
 
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1996 FWB coach
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9 Posts
Discussion Starter #18
I Got the O2 sensor in, says code PO 134 still failed. Originally codes #134, 154, and 300 showed up. I Always thought the motor seemed to run hot to me, I put in a new thermostat, and codes #8 and 24 (on ac unit), read good(90-195). The hose leaving the thermostat never seems to have pressure but gets hot, and now my overflow box seems to have sprung a leak. Possibly the waterpump? The thermostat did have calcium buildup...
589920
 

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1996 Fleetwood hearse
1996 Cadillac Fleetwood Superior Coach Hearse Conversion
Joined
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139 Posts
P0134 is Bank 1 Sensor 1 which should be before the cat. I believe that is on the driver's side or where spark plug one is. P0154 is Bank 2 Sensor 1 which is before the cat. P0300 is random multiple cylinder misfire. With that you should get a fuel pressure gauge and find out what your fuel pressure is at the rail. The P0134 and P0154 may be due to the P0300 which is possibly a bad component in the fuel system.
You should invest in one of these to be able to monitor your Oxygen sensor voltage along with temperature, and other items:

Before you start swapping parts out, those voltages on the upstream and downstream oxygen sensors can indicate what is going on with the fuel to air mixture. They fluctuate but should be within a specific range. Another thing, looking at the crud in there, I'd suggest running some sort of flush through the system multiple times and fully draining it. I used an air compressor to blow as much of the water and junk out from the thermostat opening, but really you are supposed to drain it at the block. It is possible that someone mixed green and red or another color and red antifreeze and that is what that build up is. You need to make sure the system is clean, including the radiator because you don't want to overheat and mess anything up.
 

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1996 FWB coach
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9 Posts
Discussion Starter #20
Well, found out it was the wrong cap on the overflow box. It was a 15psi, not the 18. So that fixed the water problem. Got both upstream O2 sensors on and codes cleared. And new key made, no more pass key fault. Now it's the transmission...guy before me put a new one in about 3 years ago, has less than 300 miles on it, and the car had sit a year or so. Transmission was fine at first. Once actually driving it, realized it was LOW on fluid. Now, almost 2 quarts later, finally showing where it should(sometimes, its anywhere from cold line to 5" above hot). And when it's hot, I have to manually shift from 2->3->D to move after dropping under 20 mph. Other than that, transmission shifts fine other than between 50-60 before overdrive kicks in. Shakes a bit like hiccups. But if you give it more gas, it goes into overdrive and the other gears just fine. No clunks, no lunges, nothing. Fluids fresh red, so it's not burnt up.. 🤷‍♀️um, any ideas?
 
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