Where is "Perform self-diagnosis (Mode IV) for engine control?

[jeff33]

I have a 1992 Q45. Using my service manual I am running the transmission self-diagnosis. On page AT-58 I am directed to "Perform self-diagnosis (Mode IV) for engine control. Check idle switch circuit." (This is related to the idleing and tranmission problem I posted earlier)

I cannot find the Mode IV self-diagnosis. I can find the Mode I and Mode II in the EF & EC section of the manual.

Can anyone tell me where the self-diagnosis Mode IV is located in the service manual or else give/post a copy of this procedure.

Thanks

Jeff

[elwesso]

There is no mode 4.... Just mode 1 to check the codes and mode 2 to check the o2 sensors....

[elwesso]

im trying to figure out what your doing, can you tell me what section of the FSM your looking at in the AT section (because i have the big FSM and the pages are different than the little one youre probably looking at)

[elwesso]

Ok I think I know whats going on.... PLEASE DO NOT POST MORE THAN ONE THREAD OF THE SAME THING. No big deal, but please dont post duplicate threads anymore, its really confusing me... Ive read all 4 of the threads that you created (deleted the most recent one in the VH/VK forum)..

with that aside, did you do the Transmission self diagnosis.... zerothread/217453

Im going to be updating that article with a list of codes....

best place IMO to measure the TPS voltage is at pin 34 and 35 of the TCU.. You can measure it at the ECU to put pin 34 and 35 are really easy to find...

Click the picture to enlarge.

[goody90q45]

I'm looking at my 94 FSM and it looks like you are performing the ENGINE CONTROL CIRCUIT CHECK. It's on page AT-55 of the 94 FSM although there is no reference to Mode IV.

It looks like this self-diagnosis procedure is to first check continuity between the TCU terminals and the ECU. If you've done that portion the step I think you are asking about is a check to verify the ECU is operating properly. This is where my FSM refers to EF & EC diagnostic procedure #8 which is checking the ECCS control module (ECU).

If you're not running the self diagnosis of the engine control circuit then just forget I ever made this post. (LOL) The diagnostic tools built into the Q are a great thing but they can be very confusing. Good luck.

[jeff33]

Thanks for removing the duplicate posts.

ALso, thanks to all of those following this post and providing input.

Here is what i have done.

I ran the transmission self-diagnosis without consult. The diagnositic information display never changed from "AT CHECK" which informed me that the damaged circuit is "inhibitor switch, 1 range switch, kickdown switch, idle switch or diagnostic information display system circuit is disconnected, or A/T control unit is damaged."

Per the instuctions, I am to "Go to inhibitor switch, 1 range switch, kickdown switch, idle switch or diagnostic information display system circuit checks."

I ran the checks and found the following:

(1) the inhibitor switch circuit is OK (checked voltages of terminals 16-20 for various shifter positions).

(2) the 1 range switch circuit is OK (checked voltage of terminal 39).

(3) the kickdown switch circuit is OK (checked voltage change of terminal 41 with depressing/releasing of pedal).

(4) the idle switch circuit is N.G. (no voltage change for terminal 14 when changing pedal position).

Based on test #4 being N.G., the flow chart directs me to "Perform self-diagnosis (Mode IV) for engine control. Check idle switch circuit."

THis is where i am stuck - i don't know what Mode IV is or where to find it. Perhaps it is a typo (i have found numerous ones over the years).

So, if someone can direct me as to how i can check the "idle switch circuit" I would be very grateful.

I am excited that this is where the self-diagnosis is heading because I am having serious high idle problems that occured at the same time as the transmission malfunction (during the injector change).

Thanks for your help.

[goody90q45]

.....Per the instuctions, I am to "Go to inhibitor switch, 1 range switch, kickdown switch, idle switch or diagnostic information display system circuit checks."

(4) the idle switch circuit is N.G. (no voltage change for terminal 14 when changing pedal position).

Based on test #4 being N.G., the flow chart directs me to "Perform self-diagnosis (Mode IV) for engine control. Check idle switch circuit."

In my 94 FSM everything reads the same except the idle switch is referrred to as the closed throttle position switch and there is no reference to Mode IV.

It looks like they are trying to get you to perform the Throttle Position Sensor Circuit Check. With luck this check is referenced, under the same title, in your 92 FSM. Hope this helps. Good Luck.

[elwesso]

Check your TPS voltages as I outlined.... on pin 34 and 35 and see what you come up with. The ECU/TCU doesnt care so much about the open/closed position as it does the actual position.

[jeff33]

Wes,

I checked out the Throttle position sensor and it appears to be working fine (check voltage at the connector harness for 2 different pins, checked continuity with the ECU and checked the resistance as a function of pedal position).

I am going to check the voltage at pins 34 and 35 (i think the actual pin #s for a 92Q are different). What voltage am i looking for? Also, should I be checking the voltage as a function of pedal position?

Thanks

Jeff

[elwesso]

Wes,

I checked out the Throttle position sensor and it appears to be working fine (check voltage at the connector harness for 2 different pins, checked continuity with the ECU and checked the resistance as a function of pedal position).

I am going to check the voltage at pins 34 and 35 (i think the actual pin #s for a 92Q are different). What voltage am i looking for? Also, should I be checking the voltage as a function of pedal position?

Thanks

Jeff

Yeah, you are looking for about .44 volts fully released (say between .4 and .5 being OK) and then it should slowly increase to over 4 volts...