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Weird Issues that I think are happening because of a faulty ECM? (92 cutlass S 2 door)


Bjankins1
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So I am having all sorts of issues with this car that I cannot figure out at all

For one, my coolant temperature sensor does not work, I can't tell if the sensor is bad at all, weirdest thing is, the temp guage on the cluster will moves when the key is out into the ignition and for a split second, it will move, and sometimes I can get it to go all the way to the red and stay there when the key is just far enough before starting the car, of that makes Amy sense....

Now this should be throwing a code 14 or 15 I think, but the service engine light will not come on for it, it will come on when the car is in accessory, but not when it's running, the OBD 1 reader does work, but throws only a code 12, like normal, and the radiator fans kick on normally too which leads me to another huge problem 

 

The radiator fans do not operate correctly, I've seen this car run really hot and what's scary is it's still going but I'm watching the cooling lines literally look like they are about to explode, and it's not one hose, no no no, it's almost every single hose on my car, so the pressure is insanely high, which is just great, and the fans won't work when they need too

I will mention that there is some coolant loss and I've noticed a hose that just looks it drips right under the front passenger control arm

I need a block test but haven't had the money for it, this car was a mystery and I can spend countless hours telling u every screwed part about this particular car, the last owner was not to nice to it, I'll just say

 

 

 

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Posted (edited)

Also I have the strangest issue that my gf and I cannot figure out, the car is blowing hot air constantly, it's California summer out here and it's unbearable in the car alot 

 

 

 

Edited by Bjankins1
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I plan on getting a block test and when I get home I'm gonna bleed the cooling system

Anybody got any suggestions on this whole matter

 

 

 

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On 7/8/2022 at 9:15 PM, Bjankins1 said:

my coolant temperature sensor does not work,

There's one sensor for the dash gauge, and one for the computer.  I'd be looking at the sensor AND THE WIRE HARNESS for the dash gauge.  That's more likely than a failed gauge, although that's a possibility.

 

On 7/8/2022 at 9:15 PM, Bjankins1 said:

Now this should be throwing a code 14 or 15 I think, but the service engine light will not come on for it, it will come on when the car is in accessory, but not when it's running, the OBD 1 reader does work, but throws only a code 12, like normal,

Forget "code readers".  Connect a real scan tool, look at the data stream.  Verify every sensor, find out how hot the computer (not the dash gauge) thinks the engine is running at.

 

On 7/8/2022 at 9:15 PM, Bjankins1 said:

and the radiator fans kick on normally too which leads me to another huge problem 

The radiator fans do not operate correctly,

Which is it?  The fans work normally, or they don't operate correctly?

 

On 7/8/2022 at 9:15 PM, Bjankins1 said:

I've seen this car run really hot and what's scary is it's still going but I'm watching the cooling lines literally look like they are about to explode, and it's not one hose, no no no, it's almost every single hose on my car, so the pressure is insanely high, which is just great, and the fans won't work when they need too

How old are the hoses?   Hoses get weak when they're old enough to have deteriorated.   Go to a parts store that has a loaner-tool program, rent/borrow their radiator pressure tester.   Find out how much pressure the system has when it's hot.  About 15--16 should be normal--it'll say on the radiator cap.

The cooling fans won't come on until about 220 degrees.  That's normal.

Kinda thinking one should come on with the A/C, though.

 

On 7/8/2022 at 9:15 PM, Bjankins1 said:

I will mention that there is some coolant loss

Pumping up the radiator pressure tester should help locate the leak.  Sometimes the leak is INTO the cylinder(s), so you'd want to remove the spark plugs during this test.  When the system has been pressurized for awhile, crank the engine and see if any coolant blows out of one or more plug holes.

If this is a 3.4L DOHC engine, pay special attention to coolant entering #1 and #6 cylinders.  I don't know of any particular weakness of the 3.1L engine.  The Iron Duke four-popper is a friggin' nightmare.

 

On 7/8/2022 at 9:15 PM, Bjankins1 said:

I've noticed a hose that just looks it drips right under the front passenger control arm

Coolant, or condensed humidity from the A/C evaporator box?  Water coming out of the A/C evaporator box is entirely normal when the A/C is working.

 

On 7/8/2022 at 9:15 PM, Bjankins1 said:

I need a block test

What is a "block test"?

 

On 7/8/2022 at 9:25 PM, Bjankins1 said:

Also I have the strangest issue that my gf and I cannot figure out, the car is blowing hot air constantly, it's California summer out here and it's unbearable in the car alot

Does the A/C work?  WHERE is it blowing hot air?  From the radiator fans?  From the HVAC fan/ducts?

 

22 hours ago, Bjankins1 said:

I plan on getting a block test and when I get home I'm gonna bleed the cooling system

I don't know what a "block test" is.  The 3.4L DOHC engine has cooling system bleeder screws, I don't know about the 3.1 or 2.5 engines.

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A block test is a pressure test, just used to calling it that cuz that what folks on the Cadillac forums say, I'll have to check under the dash when I get home, it's the 3.4L, where can I get a scan tool and where are the wires located that sends data from the engine to the ECM? I mean this is the strangest thing but I got it to work one time and it read a code 15 and the service engine light stayed on while driving but it has never came back after shutting the car off, the radiator fan issue is a mystery, correct me if I'm wrong but when the fans kick on when the OBD1 reader is being used, isn't it being used from a different relay, that is what i have at least read but I could be wrong

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Adding onto the list of crap, I forgot to mention the catalytic converter has a problem, it rattles and appearently the baffle is broken, that's at least what my mechanic told me, the other thing I just found out is there is a oil and coolant leak right next to the harmonic balancer, basically the passenger side at the bottom of the engine 

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If the cat is rattling from the inside the substrate has melted down, time for a new cat.

Oil leak near the dampener...most likely the front seal, outside possibility that the intermediate shaft seal is leaking, but you can't see that as the front of the engine is hidden.

Give the engine a hot bath to remove all of the leak stains and wait for them to reappear.

Edited by 55trucker
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On 7/11/2022 at 9:20 PM, Bjankins1 said:

A block test is a pressure test, just used to calling it that cuz that what folks on the Cadillac forums say,

A pressure test will verify the entire cooling system, not just the block.  Block, heads, water pump, radiator, heater core, coolant passage in the intake manifold, and all the hoses, seals, and gaskets that connect them.

On 7/11/2022 at 9:20 PM, Bjankins1 said:

where can I get a scan tool

I bought mine from eBay, used.  I currently have a Snap-On Solus Pro with various vehicle connectors and cables, rechargeable battery and charger, user manuals on DVD, and a bigass suitcase to carry it around in.  8.2 software good for 1980 1/2 to 2007.  Have had this for perhaps six months, cost $350 delivered to my door.  Newer software is nice, the newest available would be on the order of 16.4, 2016 4th Quarter. 

I bought the Solus Pro because my previous scan tool got gasoline spilled on it and was damaged.  I used that tool (Snap-On MTG2500) for about twenty years.  The '2500 series works well enough on these vehicles if you have the software cartridge and connector appropriate to the vehicle; but is much less sophisticated than the Solus family; and most of them won't graph the sensor outputs which is a significant disadvantage.

Snap-On does not support the '2500 series, the Solus or Solus Pro.  Support just ended (or is about to end) for the Solus Ultra.  The Solus Edge and Solus Legend can still be updated to the most-recent software, the others cannot.

There are other brands of professional-grade scan tools, plus a dozen brands of consumer-grade junk, plus "free" or low-cost software that runs on a laptop computer connected to the vehicle via the USB port, and a cable having USB on one end and the GM ALDL connector on the other.  I have ZERO experience with any of those; all my scan tool experience for 20+ years has been with Snap-On.

On 7/11/2022 at 9:20 PM, Bjankins1 said:

and where are the wires located that sends data from the engine to the ECM?

In the engine compartment, with the ECM.  ECM is on the passenger front fender.

On 7/11/2022 at 9:20 PM, Bjankins1 said:

when the fans kick on when the OBD1 reader is being used, isn't it being used from a different relay, that is what i have at least read but I could be wrong

I'd expect at least two relays, perhaps three.  If your code-reader triggers one or more, I suppose that would test the computer's ability to control that relay, and the fan motor's ability to spin the fan (not damaged, wire harness problems, etc.)

I'm thinking the first fan comes on at 220 degrees, the second at 230.  One fan probably comes on with the A/C.  But it's been so long since I've messed with that that I'm not completely sure.

While you're on eBay looking at scan tools, pick up a Genuine GM service manual with two or three or four books (not just one book)

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Well I've come to the conclusion that this car was to neglected and treated terrible before it got to me, and I've decided to part ways with it, it's on the market now, the car only has 122,000 miles on it, plus my GF and I have a 95 4runner that has just been sitting and needs a lot of attention, and we both have came to the conclusion that it would be worth more to fix that up over the Oldsmobile

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From what I’ve read of the issues your car is having my thoughts go toward you needing to do a thorough coolant system service.
Your rad cap is stuck/corroded on, the car overheats, it’s thrown a code 14 which is high temp.  If it runs alright I wouldn’t worry much about the ecm or cluster wiring yet.  If it’s throwing a code 12 and the fan comes on when reading the codes your ecm is good.  
id suggest buying a new rad cap, taking the old one off and see what’s up in there. It could be the previous owner was a nimrod and mixed coolant types and you have a gelatinous mess in there, it’s really old, not the proper mix, your thermostat is pooched, etc who knows until you take a look. Hopefully it just needs a service. The fact it ‘ballooned your hoses’ and over pressured could indicate a head gasket leak but start with the coolant system itself.

the ALDL port will tell you what the ecm is doing with a proper scan tool instead of a code reader(paper clip). I have an ALDL to usb cable that connects to your laptop with tuner pro. Much easier and cheaper than a proper scan tool.  Go to moats.net to get one. I’d say your wasting your time there though check the cooling system first.

I’ve attached the troubleshoot for code 14 and 15. Won’t be much use though if you can’t see the actual temp readout from the ecm.

 

 

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Edited by GTP091
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 Round 2… after you service the cooling system. It’s not likely there’s anything wrong with these wires unless some monkey messed shit up. So you’ll be r time and possibly breaking stuff if you don’t do the easy part first.

Provided you have a digital voltmeter.  You can check the continuity of the wire from the ecm to the coolant temp sensor to check for short or open circuit.  Circuit 410 is yellow. Do this with the battery disconnected.

1. Unplug the coolant temp harness.

2. Probe the black wire for continuity. If you get nothing you have a broken ground wire from the sensor to the ecm.

2. Unplug green harness from the ecm ( getting to the ecm is a chore in itself)

3. probe the yellow wire from the sensor harness and C16 of the ECM harness with your voltmeter. If you don’t get continuity you have a broken wire. 

4. Probe C16 on the ecm side and put the other lead to ground. If you get continuity you have a short.

Pictures of the ecm and harness are below (from a 91) The first and last are all you need for this test.  Be very careful handling the wires and harnesses they’re old! 

after you put everything together and reattach the battery remember to reset the IAC valve by cycling the key on and off 3 times. Engine may start and die immediately if you don’t.

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So thank u for all of this, ill have to deeply read all of this and go from there, I was able to remove the radiator cap which when I opened it up was almost like it was overfilled, because there was still pressure built up even after almost 5 hours of the car cooling down, but it spilled a bit and was able to get the cap back on, the ECM I think is actually located in the glove box on my car, when I looked under the reservoir, I didn't see anything but a random blue and green wire that was left with no where to connect them, they are not connected to a harness 

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4 hours ago, Bjankins1 said:

I was able to remove the radiator cap which when I opened it up was almost like it was overfilled, get the cap back on, the ECM I think is actually located in the glove box on my car,

One will always get fluid from the rad cap neck when the cap is pulled because the rad cap is not the highest point in the cooling system.

Glove box?!

hope not, if so you've got a mess of wiring to relocate, the ECM is under the coolant recovery tank fastened to the right side shock tower.

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8 hours ago, Bjankins1 said:

So thank u for all of this, ill have to deeply read all of this and go from there, I was able to remove the radiator cap which when I opened it up was almost like it was overfilled, because there was still pressure built up even after almost 5 hours of the car cooling down, but it spilled a bit and was able to get the cap back on, the ECM I think is actually located in the glove box on my car, when I looked under the reservoir, I didn't see anything but a random blue and green wire that was left with no where to connect them, they are not connected to a harness

Still pressured up is not a good thing after it’s cooled down. If you have to much air in the system there is a bleeding procedure that could help out here and also let you know if the thermostat is opening.  I’m hoping for your sake this pressure build up is not a head gasket leak. The 3.4 is a stout engine and not common to have a head gasket leak.  Leaking intake manifolds, yes.  

theres two brass bleeder screws; one on the thermostat housing neck right before the upper rad hose - the other on the small hose coming from the intake manifold, to the right of the brake reservoir. Do this engine barely warm not hot. The thermostat won’t be opening yet if it actually works.
 Very carefully open the upper bleeder  a few turns with a 7mm socket (they’re brass and break easy) if it seems stuck stop and give it a few small love taps to hopefully break the threads loose. If you break the head off you can still take the housing part off with a. 10mm to bleed but it may develop a leak (brass to steel) if you don’t use sealant after. 
Start the car, open the lower bleeder only, as it gets warm it’ll start to spew coolant open and close it several times when it seems a steady stream close it.
Go to the upper bleeder. Do the same here as the thermostat starts to open the system will start to spew more and more. You’ll need to wait a bit more for the thermostat to open up fully to get a steady stream.  As it warms up If the lower bleeder never starts to spew coolant in spurts the thermostat is likely stuck closed. If that’s the case the plenum will need to come off to change it. Go back and forth to both bleeders to get as much air out as you can. When they both piss coolant out quickly and steadily  you should be good.
You’ll hopefully notice a drop in the level of the coolant in the rad after it cools down.  Fill it back up.
I’d still suggest a complete drain and fill before you bother with this so you know the condition of the coolant.

rad cap must stay on for this. Only one bleeder open at a time.

if you want the drain and flush procedure i can post it up. The GM way is a bit overly complicated.

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So I have been thinking about bleeding the system, but just need a place to do it at, this car has to have a faulty ECM, the car will randomly die sometimes and start right back up no problem, appearently a common issue of a faulty ECM, happened while I was turning, went from turning normally to turning a boat, pretty scary tbh 

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That my friend is a classic symptom of a dying crank position sensor or something up with the ignition pack. Ignition control module or faulty wiring.  Bad coil will usually give a miss so I doubt it’s that. Could be ECM though.  You’re going to have to get you hands dirty and take this one at a time.  Post up some pics of your car.
if you getting a code 12 your ecm should be good.  
Here’s what GM says about ECMs. And how to replace one, read the functional check part first (last pic)

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ok I'll be honest. I didn't read the blocks of text after the OP

let me go point by point: As I recall these cars have 2 temp sensors one for the gauge cluster and one that tells the computer whats going on. not 100% on that one

either way all that actually matters is what the ECM thinks it is. do you have any means to get that data from the ECM? Tech1/2 or other scantool?

Without knowing what its actually running temperature wise. You could be falling victim to how the ECMs were programmed for fan turn on times. They run HOT from the factory before the fans turn on. Could the hoses just be worn out 30 year old hoses?

Coolant loss is most likely the pipe that runs from the front of the engine back around the firewall to the heater core. fix that before you bleed.

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  • 2 weeks later...

Not gonna lie, my girlfriend and I were a little upset about selling the car, this 19 year old kid bought it and guess what? He got caught speeding 4 days later, with no insurance, never went to the DMV and got the car impounded, now the car is sitting in a tow yard, so sad, that car could have had the potential to be a good car, if we had the money to keep it, I would have put ARP studs in, new bearings etc

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