?90 745T, error code 131 no spark?!?

Hope someone has some insight or can at least feel my pain....

In the last several weeks the car started to intermittently stop running.
If we let it sit and cool down it would then restart.
After a few weeks, the car would not restart after cooling.
But if it sits for days and days, occasionally it will start up immediately.

When the car runs, it runs strong.
When it stops running it shuts down immediately.
When it won't start there are no signs of starting beyond the cranking/ rotation of the engine.

We put in a new fuel pump&filter, cleaned up the in-tank fuel pump and filter, and the main fuel pump relay & radio suppresion relay and associated wiring/connections are all good.

In all cases when the car does not run the fuel system is producing ample pressure and the engine has no spark.
The OBD error code 131 is present and no other error codes are displayed.


Things we have done or checked or observed:

1) new crank position sensor --- changing between the old one and new one makes no difference
2) coil: the coil ohms out just fine. I got another one from a junk yard that ohms out fine. as with the CPS, if we interchange the coils it makes no difference when engine is in the mood to run or not running
3) ignition control module: same thing as the CPS and coil --- We have two of them and changing between the two makes no difference running or not-running.
4) the coil has power to it when the ignition is on
5) when the engine is in the mood for running if I wiggle all the ignition related wiring at and between the components, nothing happens (was hoping to find a bad connection)
a) ignition coil
b) CPS and connectors
c) ignition module
d) EZK 116 box near brake pedal
e) ECU passenger side of car
f) fuse / relay panel (just kind of tapping and wiggling that whole assembly to see if there was in intermittent connection in there somewhere)
g) took apart the EZK 116 and looked it all over: solder joints look good and there are no signs of anything having burned up
h) send the ECU to Programa company who tested it and said it tested fine. They also said that the EZK units typically do not go bad and a visual inspection should be enough to confirm that the EZK unit itself is OK

I took the Ignition control module and heat sink off and cleaned all of that up before putting it back together.
The multi-pin grounding assemblies: one near the ignition control module and one near the ECU --- took them apart and cleaned up and reinstalled with conductive paste
removed, cleaned and reinstalled a few other grounds: straps to cam cover, one near the EZK

Cleaned all connectors on the ignition system components including on the EZK and ECU boxes and their connectors.

And right now the car is running fine but I don't trust it to drive anywhere but around our neighborhood.

Any suggestions on next steps to diagnose the root cause of my problem and fix it will be greatly appreciated!

Thank you

Sounds like you have a bad wire, or bad connector pins on the wire. The ECU 1-3-1 error code is related to the ECU not seeing a tach pulse from the EZK. On the 240s, EZK pin 17 goes directly to ECU pin 1 (pin 1 is the closest to the metal connector retention latch). On the 740s, I think the same EZK to ECU wire goes through both the big A and B pillar connectors. You'll need to find a greenbook that shows the connectors (you might be able to use a LH2.2 greenbook if you can't find a 1990 740 one).

I'd disconnect the ECU and EZK then look very carefully at EZK pin 17 in the harness connector and ECU pin 1 in the harness connector. They should look just like all the other pins. If you have a single scrap blade connector of the same size, you could _very_ carefully insert and remove the blade from those harness pins to see if it feels tight. If the connector pins are damaged, 240turbo.com has replacements.

If the ECU and EZK connector pins seem OK, given everything else you've done, I'd cut the wires at both ends and splice in a direct EZK to ECU wire bypassing the A and B connectors.

Edit: let's go back a step first. When you get the ECU 1-3-1 code (hole #2 on the diag block), I'm assuming that you're getting a 1-1-1 code on the EZK (hole #6 on the diag block), correct? If you're not getting the EZK 1-1-1 code, are you getting anything? If not, then EZK power may be bad.

Main fuse number 1 behind the ash tray and shifter. It is the one that provides the power to the ECU. The connections in there for the fuse can get corroded clean that. I had to replace mine. I just went to napa and got a 30 amp fuse holder and wired it in. Check that. On my 1990 745 wagon the previous owner replace the whole fuse panel thingy under there in the past to fix that problem, but I just replaced the one fuse socket.

On my car I think it might have something to do with the aftermarket alarm wired in... Battery will go dead after a week or two just sitting.

Thank you for the detailed and thoughtful replies!

Yes, the error code from the ECU reads 1-3-1 and the EZK reads 1-1-1.
But just for the 1st time today on two occasions the ECU produced error code 1-2-1 for the mass flow meter.
Could the MFM be sketchy and producing weird error codes?


I was able to find some wiring diagrams that line-out connections between the EZK and main ECU.
All the pins in the connectors to the ECU's as feel "tight".
I took a small zip-tie and inserted it into each pin that relates to the CPS: CPS to the EZK, pulse signal between EZK and ECU (pin 17 to in 1), and also power to the EZK.


If I disconnect the battery and then reconnect it the engine will start easily and idle fine but about 1 to 3 minutes later the check-engine light consistently comes on.

Wiggling all associated connectors and wires and I can't get the motor to skip a beat much less die altogether.
Seems very strange.

I pulled the radio and looked at the underside of the fuse assembly.
Nice and clean.
Zero corrosion.
Pulled wires that connect to Fuse 1 and scuffed up connectors at the fuse side and wire-side.
Then applied some conductive paste and put it back together.
That was all in better shape than i would have guessed.
With the motor running I wiggled the fuse 1 wires, fuse, etc. it continued to ran nicely

Every time I touch part of this car I'm impressed with how good a condition it is in and how well made it is.
They really did a nice job with the quality of these cars.
Just have to find this gremlin of a problem.....

I did not jumper from the EZK pin 17 to ECU pin 1 just yet.
That will be next once the rain stops....

On another forum someone advised replacing the MAF sensor.
So I looked at the MAF sensor and it appears to be original or at least it is very old and a Bosch and quite dirty.

Don’t know why we never cleaned it sooner like when doing plugs and other basic tune up stuff.
After a few hours of run time no error codes and engine is running great.
Could that have been the problem all along and the ECU was tricked into reporting incorrectly?????

I’ll post back here if things change!

Thanks again for all the advice.

Hope this chain of communication is useful to someone else someday!

MAF sensor had nothing to do with it.
Replaced with a new one from FCP Euro and same error code continues to appear.

I also ran a jumper wire from the EZK to the ECU and still get the error from the ECU of 1-3-1.

The car runs great but the check engine light comes on within say 30 minutes of driving.
Always the same error code of 1-3-1.

Unlike in the hot summer months the car never dies completely ------ but I don't know why
Seems only a matter of time until it acts up again.

Very frustrating!!!
Note, I got a used EZK from a junkyard and put it in ---- the darn things behaves exactly the same ---so, that appears to have nothing to do with it, either.

Could it be a bad ground ?
Where does the EZK unit ground-out to ?

1-3-1 Engine speed signal from 01 system absent on starting

Wiring fault or RPM sensor bad

RPM sensor must be the crank sensor which also feeds the tach.

So basically the crank sensor to the ezk then it goes to the ECU? I'd look at the wiring diagrams and figure out where the bad connection is. Maybe the signal wire is grounding out killing the signal instead of a bad ground. OR could be any of the connector plugs on the crank sensor or the ezk or ecu.

When the car won't start or run does the tach move or jump when you try and start it turning the motor over? If the tach doesn't jump then it's the crank sensor or wiring from it.

The eZK grounds out through the harness it is plugged into. Some of the plugs or wires are ground. It doesn't ground to the chassis through it's body as it's body is plastic. There is a way to ground out some pins on the ezk to retard or advance the timing trick. I can't remember off hand what pins are the ground on the ezk but there are some that are.

Drag test!

bobxyz said:

Sounds like you have a bad wire, or bad connector pins on the wire. The ECU 1-3-1....

...disconnect the ECU and EZK then look very carefully at EZK pin 17 in the harness connector and ECU pin 1 in the harness connector. They should look just like all the other pins. If you have a single scrap blade connector of the same size, you could _very_ carefully insert and remove the blade from those harness pins to see if it feels tight. If the connector pins are damaged, 240turbo.com has replacements.

If the ECU and EZK connector pins seem OK, given everything else you've done, I'd cut the wires at both ends and splice in a direct EZK to ECU wire bypassing the A and B connectors.

Click to expand...

The "drag test" mentioned above is something I commonly do at the shop. I have the correct diagnostic test probes to slide into the terminals and check for proper terminal tension. Spare pins can be used instead of the special tool.

A loose terminal will cause intermittent issues.

The drag on Pin 17’s connector (female side in the connector) is looser than the others!

I looked on the Dave’s page but don’t see where they sell parts to refurb the connector.

Am I just missing something?
Could just solder a jumper wire and go pin-to-pin with a separate wire between the ezk and ecu I suppose then there would be no doubt

It can also be tricky to release the terminal. I use the correct terminal release tool. On the LH box connectors, actually, you can just lift up on a tab with a pick and then pull out the wire/terminal.

Just use a lead from a donor harness if you need to. I have a special crimp tool for putting new terminals on wires, but I prefer to get a terminated lead if available.

I commonly "string" new wiring with fresh terminals when there is an intermittent issue with that circuit.

Quick update.

I directly soldered "jumpers" bypassing the EZK connector and other connectors all together to give the EZK: 1) power to pin 5, 2) ground to pin 20, 3) connection from EZK pin 17 to ECU pin 1
(note, i also bypassed Fuse 1 with a known good fusable link and that did nothing to change the situation so it's not the fuse panel setup)

The logic here was with the error code 131 and sometimes the car losing spark all together, the main issue was either the EZK losing power or the impulse signal being lost in a bad connection between the EZK and the ECU.

so, after soldering in the power, ground and RPM signal EZK to ECU the car started just fine and runs great

but, soon into driving the check engine light came on and now with more error codes!!!!

ECU says:
3-1-2: Signal missing from knock-related fuel enrichment: wiring break between EZK pin 4 and ECU pin 28
1-3-1: Ignition system RPM signal missing on starting: wiring fault or RPM sensor bad
3-2-2: Air mass meter wire burn-off signal absent or faulty: wiring break between ECU pin 8 and Air mass meter pin 4

is it possible that the A or B pillar connectors are faulty --- can those be cleaned-up?

but what is really not making any sense to me is that on the ECU connector terminal 1 is solid - from a junked car i took a single pin (male pins on the EZK/ECU's) and gently pushed and pulled that pin into the ECU connector --- every single one of those female terminals on the connector are clean, no apparent corrosion and the "grip" the male pin securely --- pretty good drag force on the pin as it slides in and out

so, how could it still be throwing code 1-3-1???

And, why all these new bad codes?

all ideas are welcome --- it is encouraging to hear what your thoughts are as I'm getting worn down by this thing

and what still strikes me as crazy is it seems like all the wiring harnesses, connectors are perfect condition and super-high quality ---- nothing looks hacked on or corroded or brittle -- has to be something causing these issues but i can't seem to locate it!

Main/Radio interference relay connection. Round butt connector come loose at times.

changed the ECU with a newer version from a junkyard. thus far no error codes after three days of driving!!!

So, I’m thinking that despite the fact I sent the ECU off to Programa company to test it and they said it was fine a bench test at room temperature just didn’t show the failure?! Fingers crossed and thanks for support!

Reflecting back on this whole thing.....
The problem was magnified by warm temperatures and warm engine.
But it wasn’t only present when warm-just significantly more pronounced.

Guess my point is that I spent a ton of time looking for a wiring issue but maybe next time the event is heat-related maybe apply some heat with a heat gun (gently) just to see if and which components are failing.
Might allow a faster identification of the problem.

Also did some research on oscilloscopes and some day that’d be a nice addition to toolkit....less shooting in the dark perhaps.

Thanks for the followup, it sure is an unusual failure. Hope you didn't pay Programa much for their "services".

What's the ECU number that failed? The '561s have known problems with the fuel pump and hybrid circuits - see link

The faulty one is a 563 and the replacement that appears to be working OK is a 954.

From that brickboard post: “The only turbo ECU that causes problems is the LH 2.4 563. That one has a steady demand so failure must be fairly common, though not like the non-turbo counterparts as far as I can tell. Possible replacement units are 937 and 967. Other ECU failures may rarely occur but they are much more unusual than those listed above.“

Please note: to their credit ---- I contacted Programa and complained about the fact that they looked at my original ECU and said it was good.

The refunded my money 100%.
While it was inconvenient that they did not see the problem nor did they have the information that the #563 ECU was notoriously bad, they did provide a full refund.

Here is their link for anyone that may need ECU repairs: https://www.programainc.com

My 563 ecu failed, but the only symptoms were a misfire randomly during cruise and a hesitation coming off idle. I also replaced with a 954 ecu and it fixed my issues.