Ongoing problems with my GTS which is running lean at high revs. Hammer shows 2 faulty knock sensors and Hall sender and an EZK fault!
Car runs fine on a borrowed EZK suggesting that's the problem, but the Hammer still shows up same knock and Hall sensors fault suggesting these are not spurious codes from a faulty control unit.
Problem is the knock sensors were replaced nine months ago and Hall sender failure is unusual in car as young as mine - to say nothing of the bad luck required for all this lot to go at once.
Is there a common connector that could be loose somewhere. If so could you pint me in the right direction - with picture if at alll possible as this is unfamiliar territory for me.
Once again - from my shark and me - thanks!
Mark

 

the only connector that MIGHT be common would be at the fuse panel but I don't know if that is even in common. Check your timing.

 

The rear knock sensor and the Hall sensor plug into a common receptacle on the top of the passenger fuel rail - the plugs fit together on a bracket that is part of that rail. About a year ago I ran the Spanner and got "rear knock sensor broken" and "Hall sensor missing" and it proved to be this plug was loose. The front knock sensor plugs into the harness up front, but I can't recall exactly where.

[Edit after post: EGAD! The Hall sensor and rear knock sensor do NOT share a common plug. The observation that the two faults resolved by checking the connection of the rear knock sensor appears purely coincidental.]

 

Bill (facing the engine)the front knock sensor plugs is to the right of the thermostat, the rear knock sensor plug is on top of the fuel rail on the left rear and the hall sensor plug is just behind the left distributor. There is no common connector. Are you saying that they are wired together? I don't have the schematics in front of me right now!

 

OK, the wiring diagram sure doesn't support what I said. The knock sensors appear to go directly to the EZK in separate plugs and have nothing in common with the Hall sensor, but I am awful at reading the subtleties of these diagrams. I had both faults and when I fixed that plug, they went away. And my examination of the harness lead me to believe they had a common plug. Ugh.

 

Here is my interpreation. Both the knock sensors and Hall sensor are involved in retarding igntion timing. If the rear knock sensor is disconnected, the Spanner indicates that Hall sensor is missing as well. Why? Dunno. BUT I will go out the garage momentarily and re-check this by pulling that connector and seeing what faults are reported.

 

The main EZK 35-pin connector is - as far as I know - the only common connection between all of the EZK, Hall Sensor and Knock Sensors. Besides ground that is.

I'm very interested in what I will now call "GTS EZK Frying Syndrome" or GEFS for short. Is this not the second or third GTS we've recently seen with EZK and Hall/knock sensor problems? My GTS has already had the EZK replaced along with a 'repair to knock sensor harness' according to PO records. And as of its last test with a Spanner (which wasn't able to complete the test procedure) the GTS was registering knock sensor faults - IIRC.

I wonder if there is some common failure mode in GTSs? It just doesn't seem right. The older cars seem to never fry an EZK. While the GTSs seem to? Somthing's different.

I've compared the wiring diagrams for the '94 with the '91 and the diagrams seem to show that the systems are (documented as being) wired the same.

I note for the first time that there are some loops and dashed-lines on that part of the diagram.
Question: Do the loops (see L-82 of any Sheet 10 diagram) indicate shielding?

I'm a little confused by this description. The bracket on the right-side fuel rail holds the connector for the rear knock sensor. It's a 3-pin connector to the main engine harness. The 3-pin connector for the Hall Sensor is behind the p-side belt sprocket and also connects to the main engine harness. Both of these are on the right-side branch of the engine harness. The front knock sensor runs through the left-side of the engine harness.

Bill, are you implying that one or more of the pins for the knock and Hall sensor are common? As far as I can see the wiring diagrams don't show this?

And reconnecting the plug cured both faults. Curious. On a GTS? Or pre-GTS?

From the diagrams it seems that all the shielding (if the loops on the diagrams do mean shielding) for the ignition stages, hall sensor, and speed sensor are tied together - but not the knock sensors.

 

This was my 89. I now agree this makes no good sense, unless the share a common ground. I'm going out to the garage and try to replicate it.

 

Worf,
My knock sensors are 11 months old - I can't believe they have both gone so quickly. And my EZK certainly seems to be the trouble - doesn't seem to retard the ignition despite receiving no signal from the knock / Hall sensors. Hence the pinking.
And finding a suitable EZK with diagnostics is tricky - I am looking at spending $2000 to sort this out properly (it's beyond my humble skills). John Speake doesn't rebuild EZK's .... yet!
Mark

 

Has anyone ever done a continuity check on a GTS engine harness? All the signals for the Hall and knock sensors come into the EZK connector on 7 of the first 9 pins. Throw in the speed sensor and that's 10 of the first 12 pins. I wonder if there was a new apprentice loom maker employed at the factory as of MY 94 that was allowed to learn on 928 engine harnesses?

 

Bill,
The suspense is killing me......

 

EZK repair coming up soon....now I have the test jig and circuit diagram ...

Mark, ypu shouldn't have to pay more than 250GBP for an EZK,doesn't have to be a GTS, it can be cloned.
I expect you were thinking of the other work that might be needed..

It would be good to check all 3 connectors mentioned. Are you quite sure Paul siad both knock sensors were faulty ?

The diagnostics are very specific. Front or rear. (or both)

 

I think I have something like that problem on my GTS. The knock sensors - at least one of them - are fairly new (a few years old, less than 15k miles) and the EZK is new as of the same time. (And both pumps are brand new, and the injectors are freshly cleaned and balanced.) But I still get pinging.

The Spanner gets totally confused with its diagnostics. Speake indicates that it is a problem with my GTS.

I think that there is some difference between how later GTSs are wired as compared to 91s or older that is leading to a higher rate - it seems to me - of EZK frying. I, too, am hesitant to stick yet another EZK into the GTS before understanding some potential root cause for this problem.

I have on my GTS To Do List the task to check continuity of every pin with every pin-out at the ECU connectors in the hopes of either finding a short in the harness or something...

It just seems that we have A LOT of GTSs that ping.

 

Yes John,
Hammer test with my ECO showed fault with ECU, Hall and second knock sensor. We the swapped to an ECU from a 91 GT and went for a half hour burn and Hammer then showed another three faults - this time both knock sensors and the Hall. Why the difference? I sure we are missing something here. £250 fair price but I want diagnostics on it for future problems and I can't find one anywhere - other than my OPC!
Worf - mine doesn't pink (as we call it) on the GT ECU.
Mark

 

I'm off to the pub!
I've got pinking on the brain...