20 Most Recent 1988 GMC S-15 - Page 8 Questions & Answers

you need to check the battery cables and clean them and clean them, or it could be the coil needs replaceing or there might be a fuse blowed somewhere.

Jump pins A and B of the GM1 connector. You can google it to see which which pins they are. Turn the key on and count the number of flashes the check engine light makes. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com! I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Fuel pump or the fuel filter.

excessive carbon monoxide is usually the result of very rich mixtures. Here are some causes for rich mixtures:
1. leaking fuel injector(s)
2. excessive fuel pressure at the injectors.
3. ruptured fuel pressure regulator diaphragm
4. crankcase fuel contamination (from leaking injectors)
5. plugged PCV valve or hose
6. closed loop control system incorrectly shifted rich (bad O2 sensor)
7. false input signal to ECM due to bad sensor(s).

the best thing for you to do is stop by your local library and get your hands on a Haynes auto repair manual for your truck wish you the best of luck Michigan Man.also like to give you this information if you every have any hard to find GM-parts its Schram auto & truck parts they only sells GM- parts 1-800-292-1032 and they website is www.schramauto.com

Hi, there are several versions depending on your location. Please select the one that matches your situation and equipment.

standard federal





high altitude federal





California




alternate california

There are transfer case vacuum switches. The button type that you have incorporate a motor at the front differential that pulls a fork in to lock it into 4 wheel. Go in neutral then try shifting and see if its comes out of 4WD .-------- Other possibility can be locking hubs getting stuck-up hard.-------- will need to be driven in a straight line in reverse about 50 feet to completely disengage the hubs. When you stop from your reverse drive, hit the brakes a little harder than normal; this helps to "unstick" hubs sometime. If you have manual hubs, you need to disengage them on your wheel hub. ------------ Sometimes driving in reverse for 50 feet will do it. Sometimes shifting into 2wd then shifting from D to R then back to D will do it.You just have to play around with it. If that doesnt help then check the linkage.The shift linkage is got stuck hard and needs to be released.--------- Try getting under it and move the lever manually.... have someone move it from 2wd to 4wd and see if it moves.If it does, try moving it further to 2wd - it should move some more, also there is an adjustment on the shift linkage, it may need to be adjusted one way or the other.....

You might try unhooking the lever at the t-case and shifting into 2wd from there and see if that works properly.If the truck has been lifted any the shifter may be out of adjustment.Try readjusting it to 4wd low and see if it gets out of 4WD.----------
But if this is not helping, then its 4WD switch problem.-------- The switch on top of the transfercase that the actuator wires plug into was damaged. Pull that switch out and inspect, if any wire got loose or switch itself got dirty/ loose.Then remove it , clean it and connect it tight and check.----------If not helping,then switch needs to be replaced.-------Check the front axle engagement switch located in the front console.Also check 12 volt at the front axle actuator and see if its giving voltage or not.--------- This will help.Thanks.Helpmech.

You have to drop the trannsmission pan. The filter can then be accessed. Be careful not to over tighten your pan bolts during assembly, or it will leak. Hope this helps, TJ

yes they are located inside the pan at the rear of valve body.

The neutral safety switch (also contains reverse lights) is mounted on the outside of the steering column behind the dashboard for column shift models. In this case it's a curved strip of plastic and metal with at least three wires attached; it goes roughly about 1/6 of the way around the steering column. Look inside the shift console if you have a floor console shifter.