Intermittent SES

[c4zr1]

I have the same problem with my 92. The SES light comes on intermittent. I drove it to a Make A Wish car show last Friday. (I do have a Haibeck chip that has my power key on all the time.) No SES light on and my power key light was on when I first left to drive to the show. By the time I drove down to the show about 10 miles the power key light went out and the SES light came on. I thought the chip would keep the power light on all of the time, but no.

When the show was over yesterday afternoon I drove the vehicle home the long way around hoping the SES light would go off. I drove it about 10 miles with the SES on and still no power. I got 2 blocks from home and the SES light went out and I had good power so I took it out for another 6 miles and the SES light never come back on.
Last year I did have my ECM rebuilt. I am thinking about taking out the chip and going back to the stock chip to see if that clears it up.
My next task will be to try and do the paper clip jumper and see what codes I get.

[gbmidyear66]

C4ZR1 - my understanding is that with the factory chip when the SES is activated - the secondaries are deactivated - so your issue with power may be the intermittent SES. Try the paper clip.

[John Boothby]

C4ZR1 - Chances are you have a vacumn leak. If you can check codes, you will know. The vast majority of intermittant SES lights are vac leaks. A vac leak will cause the secondaries to not open, which gives you the light. This includes secondary actuators and/or secondary selonoid. This is my guess.

[tomtom72]

Originally Posted by gbmidyear66

Tom

I believe that rumours of the death of the 1990 VSS are just that. I believe the VSS for post-90 cars is different.

I believe the 90 VSS is Standard Motor Products SC6 - just like this one...

http://www.ebay.com/itm/SC6-Speed-Se...a82c83&vxp=mtr

If not - I just ordered the wrong part....

Glenn

Cool! I hope that this one is for our 90's! Let us know how this turns out. Thanks for the link Glenn!


Tom

[John Boothby]

Rock Auto emphatically told me that the SC8 was the one for the ZR-1. They look the same.

[gbmidyear66]

Originally Posted by John Boothby

Rock Auto emphatically told me that the SC8 was the one for the ZR-1. They look the same.

John, I have done some more homework on the issue - you are right (but also hopefully wrong). The 25007308 (SC8) was installed for 90 corvettes with 3.45 rear ends i.e. ZR-1 (and for 3.07 and 3.33 ratios). The 25007224 (SC6) was installed for 90 corvettes with lower rear end ratios (2.59 and 2.73). There were about 5 sources I could find for the 25007308 (including the S.M.P. - SC8) - but they are ALL no longer available.

The SC6 is almost identical to the SC8 - from what I have been able to learn, the ONLY difference is the offset in the shaft that the driven gear mounts on. I understand the SC6 can be used and function 100% identical to SC8 if it is installed 180 degrees rotated (connector lock tab position reversed) to position the gear mounting shaft so that it has the same offset as the SC8.

I will find out soon enough and report.

[John Boothby]

You're right. The SC8 is for the Stock ZR-1 3.45 rear end. I thought that was what you were talking about. Sorry.

My experiance with an intermittant SES light that goes out than comes back on during decel is a vac leak. I have had this happen three times, the first I rebuilt the entire secondary vac system, then a bad out of the box secondary solenoid and finally with a bad out of the box secondary actuator. I rebuilt my entire secondary system and after I replaced the above "New parts" it has performed without a hitch.

From what I understand, when a VSS goes bad the car will not operate above 3K rpm. Just enough to limp home!

[gbmidyear66]

Hi John

I have 4.10,s - but the SC8 is ideally what I need (I have a 43 tooth driven gear on the VSS (which would dictate the SC8)

I "think" I have eliminated all my vac leaks - I have excellent IAC value now - even when engine is hot. I will re-check the secondary system though (it was working fine before I ported the plenum).

For sure my VSS isn't "dead" - car runs generally OK - but there is evidence that it is "flaky" - will know better when I get under there - but am now ready with a new sensor (unless there is something obvious with wiring, gears, etc)

Thanks for your input

Glenn

[John Boothby]

I have a couple spare SC8 (new) if you need one. $50 plus shipping to members of this net.

Did you ever check codes?

[gbmidyear66]

OK Guys, The good news is that I have confirmed you can use the SC6 sensor in the 90.

The SC6 and SC8 are identical - EXCEPT - the slots on the face of the sensor - that the sensor hold down clamp mates to are 180 degrees out of sync (see pics attached). The alignment notch on the face that mates to the transmissison housing for both sensors is in the identical spot (aligned to the electrical connector locking tab). I installed the SC6 with same orientation of the notch that mates to the transmission housing and just filed down the two plastic tabs that the hold down clamp mates to (I guess in theory the sensor could spin - but it is in there pretty tight).

I replaced my transmission fluid - and the shift into 3rd is now much smoother

The bad news is - I still have the annoying Code 24 - VSS error - which will come on during deceleration (then clear on the DIC) once the car is warmed up. I guess I am now looking at possible ECM problem? Any suggestions at this point would be welcome.