alanz123

Hi Everyone,

Can someone point me to where I can find the Check Engine Light error messages - what they mean according to the number?

Probably has been posted somewhere, but can not seem to find it.

Thanks,
Alan

Mrmerlin

there is not any check engine light on the 928 panel.
That said your best bet would be to get a copy of the owners manual

John Speake

I understand that some early versions of the digi-dash software did allow some emissions related fault codes to be displayed.

Are the codes you get 3 or 4 digit codes ?

Ninespub

I've got a '91 $$$$4 with the digi dash and I DO have a check engine light that goes on intermittently too. I lift open the hood and yup, the engine is still there. However, I have found that if I am minimally down on oil or water the light comes on until I top it off. I am sure that John Speake knows any thing else that may apply insofar as to any codes.

Paul Barrera '91 $$$$4

WallyP

The answers can be found in the '91 booklet on changes by year, found on Jim Morehouse's tech info CD set:

This won't be pretty - cut and paste from pdf docs is a pain!

The fault memory can be read via a flashing code emitted by the "Check Engine" lamp .
To initiate diagnosis, proceed as follows with the engine off :
1 . Switch on ignition ("Check Engine" sign lights up) .
2. Close full-load contact (press accelerator pedal down fully for 3-5 seconds) .
~ "Check Engine" goes out and lights up again .
Release accelerator pedal (close idle contact) .
3 . a) The flash sequence (flashing code) indicates a fault path .

Flashing code
1 2 4
Fault path
1 = Fault present
2 = Fault not present
Control unit identification
b) Note fault code and again close full-load contact for 3-4seconds .
c) Repeat step 3b until flashing code 1000 (output end) appears .
d) Eliminate fault, then erase fault memory by closing full-load contact for more than 11 seconds
("Check Engine" lamp goes out briefly after 3, 7 and 10 seconds intervals) .
Fault pathways
No fault 1500
Idle contact - short circuit to ground 1x12
Temperature sensor NTC II 1x14
Idle contact interrupted 1x15
Air flow sensor 1x21
Lambda control rich or lean 1 x23
Oxygen sensor 1 x24
Oxygen sensor interrupted 1x25
Control unit 1 x41
Output end 1000
Other flashing codes are also possible but do not represent a warning about the "Check Engine" lamp.

Note
The fault memory can also be read and erased using flashing code tester 9268 or system tester 9288 .

Important
If the idle contact was opened during starting, the "Check Engine" sign lights up . As soon as the idle contact is closed during driving, however, the "Check Engine" sign goes out after a delay of approx 4 seconds .
If the full-load switch Is faulty (short-circuit to ground) this fault is recognized and the "Check Engine" lamp comes on constantly_ There is no way of emitting the fault through the control-lamp . In this case either the fault must first be eliminated or the fault memory read using flashing code tester 9268 or system tester 9288 .

alanz123

My 1991 928 S4 has the check engine light....

Thanks Wally for your input. Here is what I am getting.

Error Code 1115 (no other codes flashing) - What does it mean? Something major (I hope not)?

Where can a "flashing code tester 9268 or system tester 928" be obtained? What is the difference between the two and which one is recommended?

Thanks,
Alan

John Speake

As Wally listed above, that is an idle switch fault, the second digit means it is a permanent fault, if it was intermittant the second digit would be 2.

My "Spanner" diagnostic tester is based on an updated 9268. The 9288 is the "hammer".

alanz123

Thanks John - I understand the code, but what does this mean? Do I need to replace the Idle Stabilizer Valve or does the "Spanner" or "Hammer" fix this issue?

John Speake

The code relates only to the idle (Throttle closed) switch, although if non-op, this will cause the Idle control loop to not operate until you fixed the switch problem.

First check that the switch appears to operate mechanically - open the throttle at the engine very slowly, and you should hear a click from the throttle switch microswitch as soon as the throttle plate opens, followed by a similar click as you release the throttle. If no click, check that the throttle cable isn't too tight.

If you still have a problem, then you need to check the throttle switch operation at the LH ECU. If you do a search on "idle Switch" then the details will be there.

You could also try a battery disconnect for a few seconds as sometimes spurious fault codes are stored. A battery disconnect will clear all stored fault codes.

alanz123

John I will do the above and get back with my results. In the mean time (stupid question), can I drive the car? Still sounds and runs good....

John Speake

No a danger to use the car. You may fid the idle speed not propely regulated.

Try the battery ground disconnect first.

Mrmerlin

thanks for the info, I stand corrected

alanz123

Update - I have done nothing as mentioned above and the engine light is out. Any ideas?

alanz123

Battery disconnected and no engine light. Will keep an eye on it.

alanz123

Hi Everyone, Code 1115 is back. Will continue to troubleshoot and take some measurements.