Hi I live on a small island off the coast of spain and own one of the only 4 corvettes on the island, a 1991 L98 c4. I bought and imported the car from Britain last year, im English, and am now having to deal with the "modifications" that the previous owners have done to it together with a couple of problems that i have inherited, so i need some help please.Firstly the Service ABS light is permanamtly lit,i have checked all the fuses, electrical connections to the four sensors etc as the service manual supplement i bought on ebay says to do but this also says that if the light is pemanantly lit you need a scanner to investigate the trouble codes. The paper clip method reveals only code 32 set relating to EGR which is not suprising as the car has the block off plates installed. how do i find out if the pump has failed or which sensor is no good without removing,checking and cleaning them up one by one.
can i use the method in the CCM code reading article posted by Andy Bogus as this said it related to 92 and 93 cars only.
Also have just purchased an AIR pump eliminator kit from Corvette Central through my brother who thankfully lives in Virginia in the U.S. A former owner has removed all the piping and blocked off the check valves each side but did not ditch the pump. The advert from Corvette Central says you can retain the original serpentine belt but having read other forum entries elswhere lots of people say you need to run a shorter one and i really need to know before i take things apart as i would need to order from the US!!!!!
Thanks for any help
Martin

Welcome to the Guru....can't tell you on the ABS question...more knowledgable Guru's will know that answer. I had a 90 L98 that I replace the Air Pump on and did not have to change the belt. It should just take the place of the Air Pump.....

Post up some pics of your car if you get a chance....we always like to see some pictures...

Welcome, Martin!

A small island off of Spain and FOUR Corvettes? That sounds like a statistical anomaly to me.

For 1991, I think you can use my method, if not, there is a way of jumping pins and reading codes for the ABS computer - it's called the EBCM - Electronic Brake Control Module.

As an aside, I would be willing to bet a sensor has failed. Or, water has gotten inside the storage bin. The EBCM and the valve assembly are both stored in the bin behind the drivers seat. If you haven't done so, open that bin and inspect the wiring and check for moisture invasion. It can come from the bottom; ie, a crack in the case; or from the top; bad weather striping.

The ABS system is very durable in these cars. Mine is all original and has 185k miles on it. And the entire system still works great. I guess a lot of it comes down to duty cycle... I don't use either ABS or ASR all that often, so when you figure that it might have been active for all of 10 miles, total in that 185k, it makes sense it's very durable!

I checked my 1992 service manual, what I don't remember is how sophisticated the 1991 system is. Do you have a 1991 Service manual? You made reference to some supplement book... If so, go to the section on ABS, and check for diags there. It might redirect you.

If not, I will check another source tonight.

There's various smog pump eliminator kits with various optimal belt lengths so you'll get various answers.

But the one you have should work with stock belt on your year. The 85s have slightly different brackets and should use a shorter belt, and the 84 can be eliminated without even using the kit.

Thanks, checked EBCM connections before all seem ok.
Manual says if Service ABS light is permanantly lit you can only use Tech 1 scanner for diagnosis, flash code method not available. Says could relate to solonoid valve problem or pump motor but i have started car once and had the light go out and stay out while driving and then come back on permanantly the next time i started it. As sensors, pumps and solonoids don't break and fix themselves i think that it still may be a wiring problem but without a scanner or the a bility to flash codes where it is i don't know, any more ideas??????
Thanks
Martin

Regarding the scanner... a few options.

Buy a scan tool and resell it after. There are some alternatives to the Tech 1, but I don't know about your specific obd1+abs application, so you'll need to do some research there. Here's some search results:

google results

Option 2 is find the diagnostic charts for the ABS codes (in factory service manual?) and start with the most common failures, and that don't require throwing parts at it, and follow the chart for those. The diagnostic charts tell you things like check for continuity on circuit B, check ohms here, ground out pin 12 and see if actuator moves, etc. These are the charts the dealer is supposed to use to avoid just throwing parts at a problem.

This is what I'd do I guess if I owned an old car in southern california that was built on an island off the coast of Spain, lol.

Give this a try your 91 vette is equiped with a Bosch abs2S used in 90-91 on the vettes. You enable flash code diagnostics mode of the abs module by jumping pin H of the diagnostic link connector to pin A and then keying-up. The Service ABS light will come on for around 4-sec and start blinking two digit DTCs. Each digit is signified by half-second-apart flashes. One second separates the digits. Codes are flashed three times with a 3-sec. pause between. Each sequence is bracketed by code 12, signifying the sequence's start and finish. A hard fail ie light right after key on normally Points to a bad relay. I dont have my Bosch abs 2s book anymore but I believe its similar to the abs2 functionally as far as relays go. It should have 2 relays on the Ebcm (one for pump one for solenoids) and one on the harness forward next to the abs module that supplies power to the module. That one is usually the culpret for solid abs fault light right after key on and no codes stored. Usually the solenoid or pump relay being bad set a solid abs fault light after the 7mph selftest that tests functionality of the pump and solenoids. Check out this article online for a few added tidbits.

http://www.corvettefever.com/howto/19239/viewall.html