92 Fleetwood / Deville Error Codes

[Crimtide]

Been driving the car around a lot more than normal lately, and as expected, the issues are starting to show up.  Just got a check engine light.  Checked codes in the fuel data center, E48 & E52 pop up.  ECM related.  Before I go buying a new ECM, I have read it could just be a bad ground somewhere.  Where can I find the grounds without having access to a service manual? 

New ECM's are inexpensive, but still would rather clean off any contacts and pray that the OE ECM is just fine.  Also not having a manual I have no idea how to get to the ECM.  I know it's up under the dash somewhere behind the glove box, but again, not sure precisely where. 
 
I cleared the codes, drove the car again, codes came back within about 25 miles of driving.

[35-709]

"Where can I find the grounds without having access to a service manual?"
"Also not having a manual I have no idea how to get to the ECM."

  Begs the question --- why not get a shop manual?
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=1992+Cadillac+shop+manual&_sacat=6000

[Cadillac Fleetwood]

If memory serves, the E48 code pertains to the exhaust gas recirculation (EGR) system, which is controlled by vacuum regulated by an electrical solenoid controlled the engine computer system.  E52 means that there has been a signal interruption between the distributor and the ECM.

You really, really, REALLY need t get the shop manual.  That is VERY sound advice. Each of the ECM codes is covered in the manual with detailed diagnosis and "fault trees" to diagnose, isolate, and correct the condition.  There is also the problem of "intermittents" which cause a code to be set, although there is no consistent deficiency which is causing it.

Charles Fares

[Crimtide]

"Where can I find the grounds without having access to a service manual?"
"Also not having a manual I have no idea how to get to the ECM."

  Begs the question --- why not get a shop manual?
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=1992+Cadillac+shop+manual&_sacat=6000

I am new to this.. inherited the car from grandfather a little over 2 years ago, just now really putting work into it.  I should buy one.  The only one I can find for a 92 fleetwood would be the CD-ROM here - https://www.ebay.com/itm/1992-1993-Cadillac-Fleetwood-Deville-Shop-Service-Repair-Manual-CD-OEM-Guide/360469988119?epid=1122167188&hash=item53edaf8317:g:G1IAAOSwEjFXdB6j&frcectupt=true 
 
Is that what I want to buy?

[35-709]

I prefer the book form ----

https://www.ebay.com/itm/1992-1993-CADILLAC-FLEETWOOD-DEVILLE-FWD-BOOK-SERVICE-SHOP-REPAIR-MANUAL-WIRING/382864447698?hash=item59247fd8d2:g:RlgAAOSw2sNbor7N

https://www.ebay.com/itm/1992-1993-Cadillac-Deville-Fleetwood-Sixty-Special-60-Shop-Service-Manual-FWD/401699253258?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D067d028293f44ec49e730e2a066abd8d%26pid%3D100005%26rk%3D3%26rkt%3D24%26sd%3D382864447698%26itm%3D401699253258&_trksid=p2047675.c100005.m1851

[TJ Hopland]

I have a 90 manual handy, I would presume it would be very similar to a 92.   

E48 is 'egr system fault' and covers 4 1/2 pages in the manual so too much to easily translate here.

E52 is 'ecm memory reset'   Basically says that the ECM has lost power for some reason.  It says check the power and grounds and reseat connectors. 

If its the same as the 90 the ECM is on the firewall above the passenger's right foot.  You just pull the carpet back and you can see it.   It looks like it would be impossible to access  but there is just one 10mm nut to remove and it kinda slides down and out and the wires are long enough that you can disconnect them after it slides out. 

Based on what I have heard so far about your issue I would not suspect the ECM.   I would first be focused on that 52 code and power issue.  If you can get rid of that code the 48 may also go away on its own.  These earlier systems were not real well isolated so you could have an issue with one sensor or common connection between various sensors or systems that don't show a code or issue with the actual problem sensor but will trip a code on another sensor that isn't actually faulty.  You would often end up chasing the wrong systems. 

If you end up getting an ECM the official 'rebuilt' ones don't come with the prom chip.  If you get 'used' ones they will often come with the prom and that prom may or may not run your engine.  Almost no chance that anything but your original prom will run the data center or digital dash.    The proms are usually not faulty and are not difficult to change.  There is a small cover on the ECM you remove that gives you access to the prom.   The prom in its holder is about 1"x4". 

[Crimtide]

I have a 90 manual handy, I would presume it would be very similar to a 92.   

E48 is 'egr system fault' and covers 4 1/2 pages in the manual so too much to easily translate here.

E52 is 'ecm memory reset'   Basically says that the ECM has lost power for some reason.  It says check the power and grounds and reseat connectors. 

If its the same as the 90 the ECM is on the firewall above the passenger's right foot.  You just pull the carpet back and you can see it.   It looks like it would be impossible to access  but there is just one 10mm nut to remove and it kinda slides down and out and the wires are long enough that you can disconnect them after it slides out. 

Based on what I have heard so far about your issue I would not suspect the ECM.   I would first be focused on that 52 code and power issue.  If you can get rid of that code the 48 may also go away on its own.  These earlier systems were not real well isolated so you could have an issue with one sensor or common connection between various sensors or systems that don't show a code or issue with the actual problem sensor but will trip a code on another sensor that isn't actually faulty.  You would often end up chasing the wrong systems. 

If you end up getting an ECM the official 'rebuilt' ones don't come with the prom chip.  If you get 'used' ones they will often come with the prom and that prom may or may not run your engine.  Almost no chance that anything but your original prom will run the data center or digital dash.    The proms are usually not faulty and are not difficult to change.  There is a small cover on the ECM you remove that gives you access to the prom.   The prom in its holder is about 1"x4".

Thanks for all the info.  Cleaned some contacts, re-seated connections, cleared codes and took it for a drive into town and back.  52 did not come back, but 48 did. 

[TJ Hopland]

There are quite a few tests related to code 48.   The code doesn't mean the valve is bad it just means that the computer isn't seeing the results its expecting.   Unlike more current systems this doesn't have a position sensor so its apparently looking at rpm changes and O2 readings to know if the valve is working and there are other things that can effect those parameters so that is why we can't just assume the valve is bad. 

I would start with checking the vacuum lines related to the EGR valve.   Get one of those hand pumps and check for leaks then check with engine running to make sure vac is getting to the solenoid.   You can also try with the engine running operating the valve either by hand or with the hand vacuum pump.   At idle opening the valve should make the engine very rough or even stall it.   If the valve is moving but its not effecting the idle the valve or passages could be clogged.

[Crimtide]

There are quite a few tests related to code 48.   The code doesn't mean the valve is bad it just means that the computer isn't seeing the results its expecting.   Unlike more current systems this doesn't have a position sensor so its apparently looking at rpm changes and O2 readings to know if the valve is working and there are other things that can effect those parameters so that is why we can't just assume the valve is bad. 

I would start with checking the vacuum lines related to the EGR valve.   Get one of those hand pumps and check for leaks then check with engine running to make sure vac is getting to the solenoid.   You can also try with the engine running operating the valve either by hand or with the hand vacuum pump.   At idle opening the valve should make the engine very rough or even stall it.   If the valve is moving but its not effecting the idle the valve or passages could be clogged.

It did start to idle rough while sitting at stop lights, etc.  I only noticed that in the last couple of weeks, when the code started popping up.  Does that indicate more of a problem with the EGR valve, is that what you are saying? 

[TJ Hopland]

The roughness could just be the computer trying to find a happy spot.   Reason its hunting for that spot is the question.  Is it getting bad info that is causing it to make bad decisions?  Its it unable to make what ever adjustment it thinks is needed because of a mechanical or electrical condition?  Could be either end causing the issue. 

EGR shouldn't operate at idle so unless its just not closing for some mechanical reason it should not be a factor at idle.  Going down the road is when it should be operating.   Computer sees the conditions are right to operate and sends a signal to the vacuum solenoid to operate the valve.   On some systems there is a position sensor in the valve so the computer says open to 30% and expects to get a signal confirmation that yes its now open to 30%.   I'm pretty sure this car doesn't have a position sensor so the only way the computer knows the valve opened is by monitoring for the effects of the valve working which I believe is primarily the oxygen sensor.   Problem is that there are several things that effect the O2 reading so we can't just be focused on the EGR.  The air fuel mixture and timing effect it so it the computer could be mistaking an EGR fault for say a fuel pressure issue. 

All its telling us now is apparently that it thinks operating the EGR should have brought what ever was making it unhappy back into range but it didn't.  We don't know if the EGR is or isn't working or if the problem is elsewhere and the EGR just doesn't have the range in it to compensate.  That is why you basically start with the easy checks like making sure the vacuum lines are all in good shape and see if when you manually operate the valve at idle that it gets really rough or stalls.   If the vac lines are good and the passages are clear the EGR is likely working and the issue is elsewhere.    There is a built in test you can do from the data center and climate control to operate the valve but personally I would start with the vacuum lines and operating it with a manual hand pump.   If there is a problem its most likely either vacuum lines or the passages clogged.  Very unlikely that its the solenoid or computer. 

How quick and smooth does this thing start?  Same both hot and cold?   These should be like any modern car hot or cold you should barely hear the engine turn before its running.  If its taking longer there are some other things we can be checking.     

[Crimtide]

The roughness could just be the computer trying to find a happy spot.   Reason its hunting for that spot is the question.  Is it getting bad info that is causing it to make bad decisions?  Its it unable to make what ever adjustment it thinks is needed because of a mechanical or electrical condition?  Could be either end causing the issue. 

EGR shouldn't operate at idle so unless its just not closing for some mechanical reason it should not be a factor at idle.  Going down the road is when it should be operating.   Computer sees the conditions are right to operate and sends a signal to the vacuum solenoid to operate the valve.   On some systems there is a position sensor in the valve so the computer says open to 30% and expects to get a signal confirmation that yes its now open to 30%.   I'm pretty sure this car doesn't have a position sensor so the only way the computer knows the valve opened is by monitoring for the effects of the valve working which I believe is primarily the oxygen sensor.   Problem is that there are several things that effect the O2 reading so we can't just be focused on the EGR.  The air fuel mixture and timing effect it so it the computer could be mistaking an EGR fault for say a fuel pressure issue. 

All its telling us now is apparently that it thinks operating the EGR should have brought what ever was making it unhappy back into range but it didn't.  We don't know if the EGR is or isn't working or if the problem is elsewhere and the EGR just doesn't have the range in it to compensate.  That is why you basically start with the easy checks like making sure the vacuum lines are all in good shape and see if when you manually operate the valve at idle that it gets really rough or stalls.   If the vac lines are good and the passages are clear the EGR is likely working and the issue is elsewhere.    There is a built in test you can do from the data center and climate control to operate the valve but personally I would start with the vacuum lines and operating it with a manual hand pump.   If there is a problem its most likely either vacuum lines or the passages clogged.  Very unlikely that its the solenoid or computer. 

How quick and smooth does this thing start?  Same both hot and cold?   These should be like any modern car hot or cold you should barely hear the engine turn before its running.  If its taking longer there are some other things we can be checking.   

The car starts instantly, every time, hot or cold.  It has for the last 2 years it has been in my possession.   That's one thing I have never had an issue with, starting it. 
 
I have in the past had a problem with the car almost dying while turning or taking off from a stop.  It wasn't like a trans slipping and not transferring power, but more like it wasn't getting fuel.  I suspected an old dirty clogged fuel filter, and that has been on my list of things to do, but I haven't had that problem in a long time.  If I am correct, the fuel filter is still the OEM filter thats been on the car for 27 years and 56,000 miles now.

[TJ Hopland]

A new fuel filter should not hurt anything and isn't expensive.  Maybe you will get lucky and it will solve some problems. 

If its got an original fuel filter that makes me wonder what else is original?   I'm pretty sure this wasn't a 100k tune up engine.  I believe spark plugs and such were a 30k item.   

[Crimtide]

A new fuel filter should not hurt anything and isn't expensive.  Maybe you will get lucky and it will solve some problems. 

If its got an original fuel filter that makes me wonder what else is original?   I'm pretty sure this wasn't a 100k tune up engine.  I believe spark plugs and such were a 30k item.   

It was grandpa's.. the only thing in his owners manual he marked as changing is the right rear actuator?  Something with the air suspension I think?  It has 56k original miles.  The only things I have changed is the oil pan, oil gaskets, AC system.