Author Topic: 1980 Eldorado Check Engine light  (Read 1131 times)

Offline steve punzo

  • Posts: 56
  • Name: steve punzo
1980 Eldorado Check Engine light
« on: September 09, 2019, 07:03:58 PM »
Hey everyone,
      1980 Eldo 368 . Had an issue with stalling recently and was found to have a clogged CAT.  Seemed to be worse the longer the car was driven (30 plus minutes).  I removed the CAT and replaced with straight pipe and new muffler.   Got the car back a few days ago, now check engine light is coming on intermittently.  Sometimes just flashing on for a second , then going right off.  Sometimes staying solid for 30 seconds- one minute. Its been in 3 times for this issue and no one seems to be able to diagnose properly.     All suggestions welcome.   

Thanks
Steve

Offline TJ Hopland

  • Posts: 10193
Re: 1980 Eldorado Check Engine light
« Reply #1 on: September 10, 2019, 12:08:05 AM »
It seems to be running well now?  Any idea what the trouble code is?   You can get the codes read out on the climate control by holding down specific buttons.   My brain is on my 90 lately so I would have to go find my 80 manual to look up the sequence but its something like hold off and warn or auto and warm,  something like that.  If the light was on there should be codes and those should give you some clues to where to look.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Offline steve punzo

  • Posts: 56
  • Name: steve punzo
Re: 1980 Eldorado Check Engine light
« Reply #2 on: September 10, 2019, 06:24:17 AM »
Thanks TJ.   I happen to have a service manual.  I'll check today

Offline TJ Hopland

  • Posts: 10193
Re: 1980 Eldorado Check Engine light
« Reply #3 on: September 10, 2019, 01:15:05 PM »
The manuals are very good for this early stuff.    All the computer stuff is explained very well since it was new to everyone.   Once you get the code(s) you then go to that section in the manual and it will give a description of what it takes to set the code and how to go about troubleshooting that specific sub system.

Keep us posted on what you find. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Offline TJ Hopland

  • Posts: 10193
Re: 1980 Eldorado Check Engine light
« Reply #4 on: September 10, 2019, 01:18:21 PM »
I forgot to add that 80 there may have been more than one manual.   I know there was an electrical manual that has very good diagrams and troubleshooting for every system.   I don't remember if there was also a DEFI manual or if that was included in the main manual.  81 I'm pretty sure it was in the main manual but then it was also standard on most models whereas 80 it was only standard on the 49 state Eldo and I think a no cost option on the Seville.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Offline steve punzo

  • Posts: 56
  • Name: steve punzo
Re: 1980 Eldorado Check Engine light
« Reply #5 on: September 13, 2019, 11:25:08 AM »
Hey TJ,
     As luck would have it, of course, the mechanic had the car for 3 days and couldn't get the light to go on.  Sorry I can't give an update.  Thank you for your time

Offline 76eldo

  • Posts: 6651
  • CLC Number: 22443
  • Name: Brian Rachlin
Re: 1980 Eldorado Check Engine light
« Reply #6 on: September 13, 2019, 01:59:09 PM »
Your mechanic probably didn’t know that when you turn on the key to the run position you hit “Off” and “Warmer” simultaneously on the climate control head and  hold them in for a few seconds until the computer goes into the diagnostic mode. It will display codes in three rounds.
Active codes first. Then two rounds of history codes. Be ready to write them down.
Either hit “”Off” or turn off the key to get out of diagnostics. The codes are in the shop manual or you can google them.

I’m glad to see that you still have the car.

Brian
Brian Rachlin
Huntingdon Valley, Pa
CLC # 22443
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

Offline steve punzo

  • Posts: 56
  • Name: steve punzo
Re: 1980 Eldorado Check Engine light
« Reply #7 on: September 13, 2019, 02:26:30 PM »
Hey Brian,  hope all is well. The car is great. We love it. The only thing it has needed the past 5 years is some AC work . Now blowing cold .  As far as this problem goes.. My mechanic seemed to think that the codes can only ascertained when the light is on, and that the computer in this car does not store trouble codes.  After reading your post, I went out to the garage , pressed and held those buttons   88 flashed first, then 38.   Please advise 

Offline 76eldo

  • Posts: 6651
  • CLC Number: 22443
  • Name: Brian Rachlin
Re: 1980 Eldorado Check Engine light
« Reply #8 on: September 13, 2019, 03:30:56 PM »
The 88 is a standard display test code.  That will come up every time.  They used "88" so you would know that all of the segments in the LCD screen for the digits are working.  38 refers to an open MAT sensor circuit.  That's Mainfold Air Temp as I recall.  I'd look at the connector abd maybe unplug it and plug it back in.  Could be an oxidized or loose connection.  If the sensor was bad I think it would stay in a trouble condition.

Bruce Roe is the Guru on these things.  If you don't see him respond to this maybe send him a message.
Hopefully you have a shop manual.  It should tell you which sensor is which and then you can look at the connector on it.

Here is a full list I found on another Cadillac forum.  Gotta love cut and paste commands:


Code
Circuit Affected

00 (E00)
No PCM systems faults

12 (E12)
No TACH Signal

13 (E13)
O2 Sensor Not Ready

14 (E14)
Shorted Coolant Sensor

15 (E15)
Open Coolant Sensor

16 (E16)
Generator Voltage Out Of Range

17 (E17)
Crank Signal Circuit High

18 (E18)
Open Crank Signal Circuit

19 (E19)
Fuel Pump Circuit High

20 (E20)
Open Fuel Pump Circuit

21 (E21)
Shorted Throttle Position Sensor Circuit (DFI)
Wide Open Throttle (WOT) Position Sensor Circuit (all others)

22 (E22)
Open Throttle Position Sensor Circuit

23 (E23)
EST/Bypass Circuit Shorted or Open (DFI)
Mixture Control (M/C) Solenoid Open (Carbureted)
MAT Sensor Circuit - Low Temp (TBI/all others)

24 (E24)
Vehicle Speed Sensor (VSS) Failure

25 (E25)
Modulated Displacement Failure (v8-6-4)
EST/Bypass Circuit Shorted or Open (HT4100)
MAT Sensor Circuit - High Temp (TBI/all others)

26 (E26)
Shorted Throttle Switch Circuit

27 (E27)
Open Throttle Switch Circuit

28 (E28)
Open Fourth Gear Circuit

29 (E29)
Shorted Fourth Gear Circuit

30 (E30)
Idle Speed Control Circuit

31 (E31)
Shorted MAP Sensor Circuit (DFI)
Canister Purge Problem (all others)

32 (E32)
Open MAP Sensor Circuit (DFI/TBI)
BARO Sensor Circuit Problem (Carbureted)

33 (E33)
MAP/BARO Sensor Correlation (DFI)
Shorted MAP Sensor Circuit (all others)

34 (E34)
Vacuum Sensor/MAP Hose (DFI)
Open MAP Sensor Circuit (all others)

35 (E35)
Shorted BARO Sensor Circuit (DFI)
Idle Speed Control Circuit Shorted (all others)

36 (E36)
Open BARO Sensor Circuit

37 (E37)
Shorted MAT Sensor Circuit

38 (E38)
Open MAT Sensor Circuit

39 (E39)
TCC Engagement Problem

41 (E41)
Electronic Spark Timing (EST) Problem

42 (E42)
Electronic Spark Timing (EST) Circuit Open

43 (E43)
Electronic Spark Control (ESC) Problem

44 (E44)
O2 Sensor Lean

45 (E45)
O2 Sensor Rich

51 (E51)
PROM Insertion Fault

52 (E52)
ECM Memory Reset Indicator

53 (E53)
Distributor Signal Interrupt (HT4100)
ECM Unit Fault (V6 Models)
EGR Valve Vacuum Problem (all others)

54 (E54)
Mixture Control (M/C) Solenoid Shorted

55 (E55)
ECM/Oxygen Sensor Fault

60 (E60)
Drive (ADL) Switch Circuit

61 (E61)
Set and Resume Switch Circuit

62 (E62)
Car Speed Exceeds Maximum Limit

63 (E63)
Car and Set Speed Tolerance Exceeded

64 (E64)
Car Acceleration Exceeds Maximum Limit

65 (E65)
Coolant Temperature Exceeds Maximum Limit

66 (E66)
Engine RPM Exceeds Maximum Limit

67 (E67)
Shorted Set Or Resume Circuit

70
System Ready - Switch Tests

71
Brake Light Switch

72
ISC Throttle Switch

73
Drive (ADL) Switch

74
Back-Up Lamp Switch

75
Cruise On/Off Circuit

76
Set/Coast Circuit

77
Resume/Acceleration Circuit

78
Instant/Average MPG Button

79
Reset MPG Button

80
A/C Clutch Circuit

88
Display Check (-.1.8.8)

90
System Ready To Display Engine Data

95
System Ready for Acuator Cycling

96
Actuator Cycling

97
MD Cylinder Solenoid Cycling

00
All Diagnostic Complete
Brian Rachlin
Huntingdon Valley, Pa
CLC # 22443
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

Offline Dave Shepherd

  • Posts: 2426
Re: 1980 Eldorado Check Engine light
« Reply #9 on: September 13, 2019, 03:48:02 PM »
Manifold atmospheric temp sensor, this sensor very little effect on performance.  Remember this  rudimentary  efi has no default or back up values for  bad or no inputs.

Offline steve punzo

  • Posts: 56
  • Name: steve punzo
Re: 1980 Eldorado Check Engine light
« Reply #10 on: September 13, 2019, 06:01:13 PM »
Thanks Brian, really appreciate it

Offline TJ Hopland

  • Posts: 10193
Re: 1980 Eldorado Check Engine light
« Reply #11 on: September 13, 2019, 08:03:15 PM »
This is the DEFI system so not the one Bruce is the master of, no check engine light on those.

That code list looks like one of the universal ones, its got a bunch of codes that are not even in the 1980 service manual.

The 80 shop manual says 38 means that the MAT sensor signal received at the ECM is too high.  Possible causes are: open MAT sensor,  defect in wiring or terminals, signal Ok but ECM cannot process. 

The first troubleshooting step in the manual is to clear the codes, disconnect the sensor and put a jumper in the harness.  This would be a short and should trigger a code 37.  If that happens the wiring should be good so its likely the sensor.  If not then there is further troubleshooting.   

Manual doesn't say where the sensor is located, my guess would be in one of the intake runners and it would be a 2 pin sensor.     Manual also does not say how it uses that sensor.    Like others have guessed I would not expect it to cause major running issues if it was not working.

80 and 81 were known for having connector issues.  Apparently based on their experience with these cars they changed to a more robust connector type for later models.

StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

 

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