Just had a lot of work done on my 81 Eldorado Biarritz. (New radiator, plugs, wires, cap, oil change, new filters, pcv, exhaust, front axles, front shocks) And now it's having a rough idle. The computer is showing a code 18 which means an "open crank signal circuit" could anyone tell me what that means?
Does anyone know what this means?
I googled “open crank signal circuit†and got this:
… code for the engine control module (ECM) detecting an open or short circuit in the crank position sensor signal wire or sensor to the ECM.
It is from this page:
https://www.yourmechanic.com/article/p2617-obd-ii-trouble-code-crank-position-signal-output-circuit-open-by-jay-safford (https://www.yourmechanic.com/article/p2617-obd-ii-trouble-code-crank-position-signal-output-circuit-open-by-jay-safford)
While that is an OBD II page I think the meaning is the same. You need to check the crank sensor to see that it is connected and the wiring is intact and not shorted. If the wireing is good, then the sensor is bad and should be changed.
Where is the crank signal sensor located??
No shop manual? Anyway early Tbi systems used the pick up coil in the distributor as a crank sensor..
Though the mechanical components of the L62 V-8-6-4 may have been sound, the system’s electronics were not. Despite Cadillac’s claims that the Computer Command Module could process some 300,000 commands per second, it lacked the programming sophistication and overall speed necessary to direct the system across all driving conditions. Cadillac released some 13 updates, all via EPROM chip, for the Command Control Module, but none managed to overcome the system’s insurmountable obstacles. Seems it could also point to a Bad ECM. If you have a wiring diagram you need to check the wires from the ECM to the sensor for continuity, and/or corrosion. I didn't know that these years had a crank sensor, thought only a throttle position sensor. You can disable the 8-6-4 feature by cutting the single black wire coming out of the trans on the side, just above the pan. It senses 3rd gear, and that's when it disables the cylinders. A friend of mine installed a dash switch to disable this feature unless he was going on a long trip and wanted better fuel mileage. Tough to get a lot of answers on a one year only engine. Good Luck!
Bobby
Excellent post, summed up the issues back then. I was in the middle of it during this time as a field trouble shooter for Cadillac. Then we really added to fire with the inexusable 4100.
Tony,
The shop manual is cheap and invaluable, you can find an electronic copy on eBay.
"Open Crank Sensor" has nothing to do with the crankshaft, it has to do with cranking the engine over, i.e. what the starter motor does when you turn the ignition switch to the start position.
You did not mention if the "Check Engine" light is on.
Page 8D-22 of the shop manual says for code 18 "IMPORTANT: If "CHECK ENGINE" light IS NOT on with engine running (other than diagnostic display) - Do Not Use The Following Diagnostic Procedure/Trouble Tree - This is an intermittent failure and cannot be diagnosed using the procedure/trouble tree. Check all connectors in the appropriate circuit. Reset diagnostics and road test."
Jeremy
If 8 cyl-only operation is desired, simply unplug the trans switch under the car. There is no need to cut wiring.
Quote from: Eric DeVirgilis CLC# 8621 on February 03, 2018, 10:06:13 AM
If 8 cyl-only operation is desired, simply unplug the trans switch under the car. There is no need to cut wiring.
To install an in-line switch there is.....
Bobby
Quote from: Bobby B on February 02, 2018, 09:40:56 PM
Though the mechanical components of the L62 V-8-6-4 may have been sound, the system’s electronics were not. Despite Cadillac’s claims that the Computer Command Module could process some 300,000 commands per second, it lacked the programming sophistication and overall speed necessary to direct the system across all driving conditions. Cadillac released some 13 updates, all via EPROM chip, for the Command Control Module, but none managed to overcome the system’s insurmountable obstacles. Seems it could also point to a Bad ECM. If you have a wiring diagram you need to check the wires from the ECM to the sensor for continuity, and/or corrosion. I didn't know that these years had a crank sensor, thought only a throttle position sensor. You can disable the 8-6-4 feature by cutting the single black wire coming out of the trans on the side, just above the pan. It senses 3rd gear, and that's when it disables the cylinders. A friend of mine installed a dash switch to disable this feature unless he was going on a long trip and wanted better fuel mileage. Tough to get a lot of answers on a one year only engine. Good Luck!
Bobby
Didn't the Series 75 run the V8-6-4 for a few years?
Quote from: cadillacmike68 on February 03, 2018, 02:18:50 PM
Didn't the Series 75 run the V8-6-4 for a few years?
From an article in Hemmings Magazine April 2008:
Bobby
It wasn't until 1981, and Cadillac's notorious V-8-6-4 engine (dubbed L62), that the idea was heard from again. The system, standard on all 1981 Cadillacs, was developed by the division and Eaton Corporation, and was installed on the Cadillac's new-for-1980 throttle-body fuel-injected six-liter (368-cu.in.) V-8--essentially a destroked, debored 472/500.
The V-8-6-4 system was designed to shut off either two or four cylinders to increase fuel mileage; this was determined by Cadillac's on-board Computer Command Module, which used sensors to monitor engine speed, EGR, idle speed, intake manifold air pressure, coolant temp, air pump operation and exhaust, and adjusted the air-fuel mixture accordingly. If the computer sensed a sustained cruise, a microprocessor (said to be capable of 300,000 decisions per second) would then signal a solenoid-activated blocker plate that physically moved the rocker arm, preventing the camshaft from opening the valve. Your six-liter V-8 would become a 4.5-liter V-6 or a three-liter V-4 at cruise, and a digital "MPG Sentinel" gauge on the dash would reveal how many cylinders were in operation. With only four cylinders doing the work, intake-manifold vacuum and pumping losses are both decreased. Fuel economy gains of 15 percent or more were realized when (or should we say, if) it worked.
That "if" is a biggie. Disaster doesn't quite cover the scope of what happened. Throttle-body injection issues paled in comparison to the valve switchgear: While the bottom end of the engine remained strong, the software needed to run the system wasn't nearly fast or powerful enough to manage the job at hand. Also, while press reports mentioned smooth transitions between four, six and eight-cylinder modes, buyers reported noticeable hesitations while the computer and hardware got their act together. To a Cadillac owner, this was an unacceptable driveability concern. Most V-8-6-4s saw the cylinder deactivation deactivated, leaving them in V-8 mode.
I hope Hemmings realizes all those issues were dealt with decades ago when all 1981 V8-6-4 cars were recalled and received a better brains and connectors.
As far as the mechanical aspects of the V8-6-4 are concerned, the local Cadillac dealers told me they never saw any problems with any components related to the valve actuation system.
V8-6-4 was used in the Limousine models from 1981 - 1984. The Limousine models did not get the Fuel Data display dash panel readout of the standard models.
Quote from: Bobby B on February 03, 2018, 11:49:39 AM
To install an in-line switch there is.....
Bobby
For that, yes.
I've owned two dozen [post recall] V8-6-4s, and never had a problem with one.
That Hemmings article makes it sounds worse than the HT4100 and a diesel combined.
True, from a basic mechanical point of view the 8-6-4 was basically bullet proof. The ecu was very slow to transition the valve deactivation, so stumbling and hesitation was common,. Traditional Cadillac owners were understandably intoletsnt of this issue. Lot of customer dissatisfaction existed from 81 forward, general quality began to fall of even more. Very fresh in my mind as I was in the middle of all this.
Quote from: Eric DeVirgilis CLC# 8621 on February 03, 2018, 02:54:24 PM
That Hemmings article makes it sounds worse than the HT4100 and a diesel combined.
I have Zero experience regarding the infamous HT4100, so I can't feel anyone's Pain ;D....
Bobby
I seem to remember there was a class action suit vs GM because of the V8-6-4 engine. I believe a few fires occurred with these engines. The basic problem is that, while the technology was a good idea, it really wasn't perfected, as it is today. The reason for the engine was to avoid a sur charge for not coming with in CAFE requirements. Cadillac rather then add a few hundred dollars to the cost of the cars, went for these engines. Like man posted. Its really a good engine if the computer wire is disconnected and the car runs as a basic V8.
Still needs the computer to run regardless of whether or not cylinder activation is disabled. Disabling did not affect the reliability of the engine either in any I've encountered. Again, all 1981s that I owned were long after the recall campaign updates had been performed.
I don't recall any lawsuit in connection with the V8-6-4 but I do know that Cadillac ultimately issued a supplemental 5 year/50,000 mile driveline warranty on all cars with the engine which would apply to any car and any subsequent owner.
Quote from: Eric DeVirgilis CLC# 8621 on February 03, 2018, 08:22:24 PM
I don't recall any lawsuit in connection with the V8-6-4 but I do know that Cadillac ultimately issued a supplemental 5 year/50,000 mile driveline warranty on all cars with the engine which would apply to any car and any subsequent owner.
https://www.leagle.com/decision/198350593nj412184
http://caselaw.findlaw.com/ca-court-of-appeal/1770877.html
https://www.newspapers.com/newspage/6380730/
Okay so just to clear up my issue, my car runs pretty much perfect, I drive it with the 8-6-4 plugged in, almost every time I drive the car my check engine light will go on and code “18†will show up in the computer. I reset it and sometimes it will go away and sometimes the code will come back. What should I look at in reguards to the engine? I had a tune up done on the car which included cap, rotor, plugs, wires, etc. I should also note the only other issue with the car is when I get gas the gas spits back up the neck. I assumed that the sending unit will most likely need to be replaced because the tank is not getting ventilated. I am only mentioning this in case it has some connection to the code 18 issue. Also I have not changed the injectors so if that helps let me know.
Tony, as was mentioned this code has nothing to do with mechanical parts, so I would disregard the tune up as a possible cause. When you turn the key all the way forward to crank the engine, a reference signal goes to the ECM. Unlike a lot of the wiring going to it, GM thoughtfully included a fuse on this circuit. Check if you have 12 volts to this circuit while cranking, then check the fuse. My bet is they will both check out ok, and the problem lies in a bad connection on the ECM. Clean up the contacts and re-seat the it.
Interesting about the stalling issue, at that time when I worked for Cadillac in NYC, we had multiple complaints about stalling, very hard to reproduce, but one common cause was the baffle in the gas tank that the pick up sat in broke loose and would block the fuel flow under certain conditions.
Tony,
Amazing how any time someone has any sort of trouble with a L62 equipped car the comments instantly go to what a disaster the engine was ::)
I have attached the trouble tree from the SM so you can give it to your mechanic. Good luck getting it sorted out.
Jeremy
Quote from: e.mason on February 03, 2018, 10:13:36 PM
https://www.leagle.com/decision/198350593nj412184
http://caselaw.findlaw.com/ca-court-of-appeal/1770877.html
https://www.newspapers.com/newspage/6380730/
Thanks for the detective work. (I only said I have no recollection;
not that it did not happen.)
If any car deserved having a lawsuit being filed over, it should've been the HT4100. :o
Quote from: jsanford on February 04, 2018, 11:03:59 AM
Amazing how any time someone has any sort of trouble with a L62 equipped car the comments instantly go to what a disaster the engine was ::)
Indeed.
Since there is a fuse in that circuit I would check that close. Recently on a much newer vehicle with that style fuses I had intermittent issues that turned out to be what looked like tarnish on the fuse blades itself. I say tarnish because it didn't clean off with a wire brush like normal corrosion. Slapped in a new fuse and all was well. The socket looked fine.
Its interesting that they put that fuse where they did. I wonder if that is maybe to protect the wire when it comes inside the car vs under the hood? There isn't likely much of a load so it won't take much of a bad connection to screw it up.
Where is that '56 way' physically located?
Just drove my car to get lunch, when I finished and started my car I was idle for about 10 minutes and I got a bunch of codes
19
23
24
25
32
44
45
I looked them up and they’re all pretty much from a short, anyone have any suggestions as to where this short could be?
Its really unlikely to have that many codes that are not related so you have to find out how they are related. Start by finding what all those codes / sensors have in common. Do they all have a common ground point perhaps? All run into the same loom? Same bulkhead connector? Same connector at the ECU?
I have not looked at them for a while but I remember the electrical parts of the service manuals in that era were pretty well written since at the time no one was used to dealing with the computer stuff. They gave a very specific sequence to trouble shoot which if that doesn't solve the issue on its own would give you indications how the things relate to each other. For instance the first like of say code 99 would be to make sure you don't have a code 77, if you have a 77 fix that first. That would tell you that what ever sensor or module 99 is likely depends on 77 working correctly.
After troubleshooting multiple codes on the “02 Buick antilock brake system, I removed all the grounds, cleaned and replaced them. No more trouble codes. Maybe you could try that.
I am posting on this thread because i just realized there may be a connection. I recently posted a thread about how my ECM fried, heres the original post...
"Okay recently I went to start my 1981 eldorado Biarritz and smoke started coming from under the glove box. I took apart the under dash cover and found the ECM was the issue. I removed it and purchased a replacement. Installed the PROM chips to the new unit and the new unit started to sizzle as well so I quickly shut the key. The issue happens when the car is in the “run†position. Can someone guide me through this issue? I cannot start the car without the ECM. The car has 70k miles and was running perfect with no issues before hand."
can someone who has knowledge on these computers let me know if theres anything that can be done?
also, I recently found a post from 2008 where someone unplugged the "Air management Valve Solenoids" from the 81 6.0 enigne and the ECM stopped the smoking. I did the same thing and had the same results, with the Air management Valve Solenoid unplugged the ECM did not smoke.
Hey, Still trying to resolve this issue, ECM completely fried, bought a new one and reseated connections, bought new PROM chips (same part number) . still cant find the short. where do it start???
I would open up the fried units and see if I can get any clues as to which system(s) have the issue. Look for burnt stuff and see if you can tell which pins in the connector they go to. Use the diagram to figure out what sensor or systems are connected to those pins. If you can't tell then you may have to just go pin by pin.
With the electrical service manual you will know what is hooked each pin and you should be able to do basic ohm meter tests to determine if what is connected to it is shorted to power or ground and often the general health of the system.
Again I would be looking for visual clues to save time by looking at the fried units and carefully inspecting all the wires and connectors I can see. Look for places that don't look factory. Look at places with heat like around exhaust. Look for places that are more exposed to road grime like down to the starter. Its pretty rare to have a wire or connector just fail for no reason at all.
Quote from: TJ Hopland on February 17, 2020, 01:15:47 PM
I would open up the fried units and see if I can get any clues as to which system(s) have the issue. Look for burnt stuff and see if you can tell which pins in the connector they go to. Use the diagram to figure out what sensor or systems are connected to those pins. If you can't tell then you may have to just go pin by pin.
With the electrical service manual you will know what is hooked each pin and you should be able to do basic ohm meter tests to determine if what is connected to it is shorted to power or ground and often the general health of the system.
Again I would be looking for visual clues to save time by looking at the fried units and carefully inspecting all the wires and connectors I can see. Look for places that don't look factory. Look at places with heat like around exhaust. Look for places that are more exposed to road grime like down to the starter. Its pretty rare to have a wire or connector just fail for no reason at all.
I've opened up the unit and I saw where the burnt area is however I am not an expert at tracing circuts to get to the pin. Ill do my best and update soon with anything I find
http://forums.cadillaclasalleclub.org/index.php?topic=157682.0
really need help with this: Replaced the Air Diverter Valve Solenoids (there was a short in one of them) Plugged in replacement computer and the car starts up, however I am getting nothing on the display for the Fuel Economy readout, the check engine light is on, and I cannot check codes in climate control display. Does anyone know if the ECMs are different between years? (yes I used original PROMS) Im wondering if I have a HT-4100 ECM instead of a V-8-6-4 ECM. If that is the case does anyone have the correct ECM for sale?
Replaced the solenoids and ecm, car runs good now but I just got a code 17 and 23; anyone know what they mean?
Wheew..... I'm not loosing my mind, there is more than one thread and many of the posts are duplicates. I knew I was mixing this up with the Italy one which was confusing enough but now that I see there are 2 of these I feel a little better.