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Ign module tach wire


ChrisWhewell
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I'm still trying to hunt down, why my tach display and temp gauge display on the IPC intermittently go out.  They do not go out simultaneously - the tach stops reading first, and if the tach keeps on not reading for more then 2 seconds, then the temp. reading disappears also.  If on the other hand the tach reading goes out but comes back on before two seconds have elapsed, the temp gauge remains constantly lit and reads the correct temp.   

 

So, I pulled the connections from the ECM and doused them with contact cleaner, followed by a generous blast of compressed air.  No help.  The grounds are all clean up by the battery, and also the ones on the manifold behind the tensioner.

 

I came across this info:  http://www.alarmsellout.com/support/diagrams/vehicle/BUICK REATTA 1988-1991.pdf

 

It says there's a purple/white wire on the ignition module.   So, I pulled the connector out.   Yuck, it was like, all gummy with some tenacious adhesive like bubble gum on a blacktop parking lot in the sun.    Sprayed and cleaned those contacts, but did not solve the intermittent tach issue.   Some have suggested its the IPC and maybe it is, but I might as well, at least exhaust all other options.


I'm wondering, whether something faulty in the ignition module could possibly cause the tach on the IPC to intermittently quit ?    I'm thinking probably not, but who knows....

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If you enter diagnostics, and pull parameter ED11 (ecm data #11) that is the raw tach data. I suspect you have an ICM failure as well since you have the green slime evident, and perhaps it is not reporting the tach data to the ECM and in turn the BCM cannot add the tach data to the data stream it sends to the IPC for interpretation and display. If ED11 shows 0 with the engine running while in diagnostics then the cluster isn't getting the tach data to begin with. 

 

Then again, you are losing the temp gauge as well. That does not get reported by the ICM but the engine temp sensor which has a direct input to the ECM. That makes me think you may have an IPC (or less likely a BCM) problem that is  causing it to drop the tach and temp data. I can't see a situation where loss of tach data would affect the display of the temp gauge. Keep in mind that all the data displayed on  the cluster is "picked off" a continuous serial formatted data stream that contains the vehicle speed, engine RPM, temp, fuel level, voltage, both the total and trip odometers as well as the state of the various status and malfunction indicators (lights on, SES, electrical problem, ABS, service A/C, headlamps suggested etc.).

 

It is possible for one or more parameters to be missing form the data stream due to a failed sensor, bad wiring, or even a malfunctioning module.  I guess my point is that you may have a bad ICM but there may be another fault present as I don't see the ICM problem being relevant or related to the loss of temperature gauge readout.

 

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I'll try that,stay tuned.   Meantime, its 99 degrees here today.   After half an hour of driving, the tach and temp gauge quit their intermittent tantrums, and are steady.   So, another clue is that apparently when the car heats up, some sort of "expansion" or other of a part, or something, is going on that is heat-dependent that makes it work normally.  I'll check the raw data, thanks alot..  (ps, I had the windows tinted last week with the 70% IR blocking film, got the AC to cycle properly, and just fixed the vent issue, it was just a loosed vacuum hose under passengers knee panel.  Plus my cam magnet is back on - NO CODES !!  She runs like a champ.   Pulled up next to a couple in a new LeSabre, they were eyeballing my baby.  My 90 reatta, IMO is better than a new one.   Why ?   Because of the know-how of all on this forum and ROJ (thanks Ronnie!!) and others - we have 95% of the bugs figured out, whereas the folk with the newer cars, their mechanics are still on the low slope of the learning curve :)

Edited by ChrisWhewell (see edit history)
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I'll concede that color matched side mirrors look good, but I've opted to keep all mine stock black so that they are easily interchanged with spares on hand should I need to replace one. Also, I think color matched mirrors might be a bit much on a white car (which all but one of mine are), and they will show dirt and splattered bugs much more than black mirrors. I find that to be the case on my DeVille, which is also code 40 white and has the mirrors painted body color. 

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I read my ED 04 and ED 11.    ED 11 is normal, even when the tach reading craps out and isn't displayed on the IPC.  

 

But get this, ED04 read 67 degrees, yet the engine is clearly hot, and its been at least 85 deg. outside the past 24 hours.   So, for some reason the car believes the temp is lower than it really is.   Faulty sensor ?  That's all I can figure.  A new one won't solve the issue but maybe will get me a little leaner operation.

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67 degrees Celsius = ~153 degrees Fahrenheit.   If the engine wasn't up to full temp. that is OK but it takes about 160F before it will go into closed loop operation. However, when I drive my car in the winter it sometimes doesn't go into closed loop for a long time and the engine still runs without problems. I have a 160* thermostat and rarely drive in the Winter when it is cold but the temp doesn't cause any noticeable driveablity problems like you are experiencing.

 

 

 

Edited by Ronnie (see edit history)
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Thank you.   I don't know why I assumed it was degrees F.   Duh.    Yes that 160 deg is the magic number, was the same also on my 1990 454SS chevy truck.   Its cool how things we learn on one vehicle apply to other vehicles sometimes.

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Something that might be of interest to you is that the ECM will start locking the torque converter at 147* (on my car). You would think that closed loop and converter lockup would go hand in hand but that is not the case. Might keep that in mind when thinking about your problem.

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On July 11, 2016 at 0:38 PM, Barney Eaton said:

I think you are getting warm..........the coil module is a fairly common problem.  Good chance that could affect the tach

 

Well Barney, trashing the Magnavox didn't help the tach display intermittent cop-out.   At least its eliminated as a potential source - I upgraded to 3 Delco coils atop a module from a 98 Riviera, Floyd let me pick the necessary parts for free from his yard.  I have a new radio coming, when I change the old one out I think I'll pull the plugs on the IPC and douse them with cleaner, see if that helps.    

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On July 11, 2016 at 11:25 AM, Ronnie said:

Unless you have replaced the module recently it may look like this inside.

 

 

ICM-magnavox-4.jpg

 

 

The previous owner had apparently put some yellow fluorescent dye in the AC.  I took a uv light out to the car last night late and found a tiny leak I had. However, I noticed also that that sticky goopy junkola that emulates from the Magnavox units also glows in the uv light, and its disposed right above the compressor.   I'm so happy to finally have that sticky mess out from under my hood.   I bought a bunch of stuff from your amazon Ronnie, your prices are really good and I like helping out your efforts.   I can't thank you and the other good guides on here enough.

 

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I'm thinking you likely have a failing cluster now. This is an unusual failure mode, one I haven't yet run across, but sure seems like the data is being dropped within the IPC prior to being decoded for display. Keep in mind the data goes through three stages prior to hitting the display:

 

1. Pertinent data is picked off from the continuous BCM data stream by the IPC CPU. At this point it is a serial list of data variables, in programming parlance.

 

2. It is then decoded by the IPC CPU and processed into a format that is sent to  series of serial to parallel shift registers with integral power darlington outputs where it is essentially converted into data that is output as parallel high voltage output signals to drive the anode and cathode inputs on the VFD display panels. 

 

3. These high voltage parallel outputs are fed into the appropriate pins on the VFD to selectively energize the grid and segment elements on the VFD for display in human readable format. The filaments on the display [run at lpwer voltage] remain energized at all times when the cluster is on. If these fail, you have no output at all (blacked out cluster).

 

So, it seems a portion of the data either isn't making out of the CPU within the IPC, or you have bad outputs on one or more shift registers IC's that are causing some segments to be dropped from the display. In either case this is a bit-level error somewhere between the CPU and the VFD digital displays (there are three seperate VGD panels within the IPC). Further, it appears to be a thermal issue since it is intermittent. The short version is you need to try another cluster.

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26 minutes ago, ChrisWhewell said:

 

 

The previous owner had apparently put some yellow fluorescent dye in the AC.  I took a uv light out to the car last night late and found a tiny leak I had. However, I noticed also that that sticky goopy junkola that emulates from the Magnavox units also glows in the uv light, and its disposed right above the compressor.   I'm so happy to finally have that sticky mess out from under my hood.   I bought a bunch of stuff from your amazon Ronnie, your prices are really good and I like helping out your efforts.   I can't thank you and the other good guides on here enough.

 

 

 

Thank you for using the Reatta Store. I appreciate it. It always makes me happy when I'm able to help someone with their Reatta.

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16 hours ago, KDirk said:

I'm thinking you likely have a failing cluster now. This is an unusual failure mode, one I haven't yet run across......

 

Yes, if the issue is with a UART data line, then I'm SOL.   But, here's a re-cap of the symptoms:

 

Temp gauge on cluster stays lit and reads mid scale when engine hot.  

 

Temp gauge instantly disappears after tach reading drops to zero and disappears.

 

When tach gauge fails, it does not instantly disappear, rather, it drops from 2000 rpm or whatever, to zero over the course of 1/4 second, graduallythen disappears.

 

If tach reading decides to come back on within about two seconds, the temp gauge reading will not disappear at all but reads constantly mid-range with hot engine.

 

So, I'm inclined to believe there is obviously some commonality between the display of the temperature gauge reading and the display of the tachometer reading, with the loss of temperature reading being dependent on the presence or absence of the tachometer being displayed.

 

Driving over the little cuts on the edge of the road that are supposed to wake up drivers who are dozing off the road, you know, those little bumps... has no effect on the tach display.  I'm inclined to rule out vibration.

 

I swapped the Magnavox for 3 Delco D555 coils and a module from a 98 Riviera, the engine runs great but the new ICM had no effect on the tachometer display.

 

Realizing the 98 Riv's IPC has all the same features as my 90 Reatta, and not having a FSM for the Reatta, I look at the FSM which I DO have for the Riviera, trying to find some common link, connection, bond, bondage, etc btw. the temp gauge and tach gauge, I can discern none.   Remember, the same ICM is used for each and they are highly likely to be very similar if not identical in circuitry.  The tach wire coming out of the ICM on the Riviera goes directly to the IPC so its probably safe to assume its the same way on the Reatta.  On the Riv circuitry, there's a connector between the IPC connector and the grommet in the firewall, and its the same on the Reatta, I just found that connector.   Next step is to open up and clean that connector in a few minutes from now.   I bought a new old allegedly-working replacement radio, and will install it when it comes today or tomorrow and at the same time pull the IPC and inspect and clean its connectors.

 

One last thing is to clean the hots connection in the little red box up behind the battery at the top of the fender.   I did all the grounds but need to get in there and do those hots.

 

The perplexing things are the apparent dependency of the temperature display being dependent on the tach display working, the temp gauge instantly disappearing whilst when the tach display fails, the reading gradually falls to zero prior to disappearing.  These are all the forensic clues I have :)

 

 

 

 

 

 

 

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2 hours ago, Guest of you all here said:

While in operation-

have you ever gently wiggled the ECM or BCM connectors around?

 

That's how I found my ...... "component cooler".B)

 

Thanks for the suggestions.   The new old radio I ordered arrived, so I installed it.   Hurray, at least I have FM radio now, and wow it sounds great.    While in there I pulled the IPC and cleaned contacts on both sides, and.... in an amazing feat of luck, it went right back in.   Didn't help the intermittent tach failure, darn it.   Actually, I could care less about the tach, its just that, when it quits and makes the temp gauge fail, that causes my AC compressor to crap out.   At least I can listen to the radio as I roast.    Where's the BCM ?   Is that the one it behind the glovebox ?  

 

Edit:  I'd be happy if I knew of a way to preclude the lack of engine temperature display from making the AC compressor stop working

 

 

Edited by ChrisWhewell (see edit history)
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I'd use the diagnostics to display the coolant temp and see if that also fails. Also there are two AC signals in the diagnostics, one for the ECM and a different one for BCM. Does the BCM stay up and the ECM goes off or do both go off.

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Some further clarification. First, do as Padgett suggested and check coolant temp in diagnostics (can't remember which parameter number of the top of my head and see if it displays irrespective of the gauge showing correctly. If so, then both parameters are getting into the cluster but the cluster is not post-processing the data properly for display on the gauges. Note that the diagnostics display on the cluster is handled by a different portion of the circuitry than the gauge "faces" so the former may show fine where the gauges themselves are not working as they are not receiving the needed display data from the shift registers (and again, these are IC's integral to the cluster). 

 

As to the gradual drop off of the tach, this is expected as the cluster has a smoothing algorithm in it's firmware to keep the gauge displays from exhibiting jitter or jumping around wildly. This makes the displays more refined, like a sweep needle on an analog gauge. Without it, the gauges (speedo and tach anyway) would be very distracting to look at.  So, if it loses the tach altogether, it wind down rather than reading 0 instantly. 

 

Further, don't make the assumption that the tach and temp gauges are dependent on each other to display. That isn't the case, it is just that in this instance your cluster has a malfunction that is affecting both concurrently. I do not think you have a UART dataline fault, and if you can pull tach and temp readings via diagnostics even when the gauges are not working, then the UART is fine as the data is being supplied but not properly acted upon by the cluster.

 

Finally, the 98 Regal FSM will not be much help in troubleshooting the Reatta. While the cluster may have similar functionalty, it is a completely different system of communication (GM Class II bus and OBD2 platform) and thus any similarities are purely superficial. Also, unless I'm mistaken, the last gen Regal has an analog cluster based upon stepper motors for its gauges, with digital odomoter and information readouts. Basically nothing notable in common with the Reatta.

 

Anyway, I'm 98% certain the cluster is the issue here. Vibration may or may not affect the issue. More often it is thermal, and as things heat up and expand open circuits occur in either marginal solder connections on the circuit board, or in a failed component like an IC. The 90/91 cluster is heavy on surface mount components and pass through joints (known as vias) on the double sided boards within. These are a known source of problems as well, and account for a lot of the issues with these clusters. I do not, however, suspect this the problem with yours. 

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I couldn't have made it, but holler at me next time maybe.   I'm dealing with my Rheem AC today, 24V present at thermostat but not at the contactor relay, traced it down to a failed solid state time delay relay.  At least I can get it to run by putting a heavy chunk of rubber on top of the contactor.    The AC techs always want to sell me a new system, until I walk them around to the south side and show them the Amana unit that has been running all seasons since 1977.....   The Rheem is only 19 years old :)    Their credo seems to be like... if your water pump goes out on your car, buy a whole new car....  they want easy bucks.  I guess it doesn't hurt to try, but I ain't their guy for that - I was raised by folks who grew up during the depression

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On July 15, 2016 at 6:02 PM, padgett said:

I'd use the diagnostics to display the coolant temp and see if that also fails. Also there are two AC signals in the diagnostics, one for the ECM and a different one for BCM. Does the BCM stay up and the ECM goes off or do both go off.

 

So, I go into diagnostic mode, to read data for ED01, ED04, ED06, etc.   I got up to ED11 (eng. speed) and it read correctly, but just then at that moment, the tachometer crapped out, the diagnostic mode reset itself back to square 1, and when I got it back around to where it read:  "EC ?" and I entered "yes" (up arrow), the message it gave was "no Ec data".  Cannot get any Ec data while the tachometer is not reading anything.  Only when the tach display is active am I able to see any Ec diagnostic values.     Its starting to sound that I don't have a bad IPC, rather an ECM with an intermittent failure, in the circuit that sends tach info to the IPC.   

 

There is also a b334 code, indicating loss of ECM communication, but it is intermittent as well.   I've already pulled the three connectors from the ECM, sprayed them with CRC followed by blasts of compressed air.   Its sounding as though I need to start hunting down an ECM...  ??

 

 

 

 

 

 

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Here's another clue.... I jumpered terminals A and B on the ALDL.   It flashed the usual code 12 three times, then gave me a ...... CODE 47.   Great.  There's no 47 in any of the tables I've seen.  I guess I'll hunt a little more for a 47 and see what that means.   It was definitely a 47.

 

 

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13 minutes ago, Guest of you all here said:

Do you still have the ECM out?

 

Just to shut me up-

 

please take the cover off,

 

and tell us what the # of EPROM it is.

 

The CALPAK unplugs just like a RAM in a PC.

 

Thank you.

 

No, I did not remove the ECM, only had disconnected and cleaned the contacts.    Are you suggesting some of the EPROMS are bad and the bad ones are identifiable by number ?    thanks again !

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a) yes

b ) there is a section in the 90 FSM at 8D1-62 for EO47 that refers to the BCM for intermittents at 8D2-32 and on the next page there is a troubleshooting diagram. Did you see any other B33x codes or just B334 ?

 

b334error.jpg

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No, its only B334, thats the only code when using A & B jumpered on the ALDL, and also using the on-board diagnostics via the climate control.  its the only code the car has.    I jerked the plugs gently on the BCM, if it was just a loose connection, the male and female parts of all the connectors have rubbed each other sufficiently it would have gone away if it were an electrical connection.    Thanks for the chart, let me digest it a couple minutes.

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10 minutes ago, padgett said:

b334error.jpg

 

When it says "DISCONNECT ECM", I suppose that means all three connectors ?   2A8.... I'm guessing that'd be the middle connector, row A, position 8 ?  Grounding that little #*&@ will likely show the problem.  Yes, I need a FSM, its just that I've been buying parts left and right :)

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Since, when I recently added a jumper between terminals L and M on the ALDL connector, it had no effect on my little intermittent tach display failure.... it seems likely that the portion in the diagram Mr. Padgett provided above that suggests an open in circuit 800 between ECM and BCM can be ignored.   What I could do is simply unplug the ECM, and then ground the jumper wire I installed between terminals L and M on the ALDL connector, that should have the same result as grounding 2A8.  It appears Nick Michels had the same problem, solved it by ECM replacement.   

 

I might try just a different EPROM first, they're cheaper.    The computer let me read the ID of my EPROM, it is 8064

90aldl.jpg

Edited by ChrisWhewell (see edit history)
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6 hours ago, ChrisWhewell said:

I might try just a different EPROM first, they're cheaper.    The computer let me read the ID of my EPROM, it is 8064

 

I believe you have the correct ECM PROM for a 1990 model. ECM PROM List

The EPROM rarely goes bad. Just based on what I've read in this thread and a gut feeling...  I think you probably have a bad ECM.

 

Take note that flow chart says to ground the pin in the "harness" not the ECM.

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Indeed.   And the contacts L and M on the ALDL connector are in effective electical communication with the indicated pin on the harness; hence I do not even need to know which one of the connector holes is 2A8. :)  But, I don't have time for any more of this nonsense, I'm just going to get another ECM.... someday when the price is right.   I'm acclimated to 100 degrees now, not having AC is no big deal :)

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