Check Engine Light

[FEF]

I picked up the Canadian '88 Suburban. I found something interesting.

It's got a button (more of an indicator light) to the left of the steering column that says check engine. I didn't think these rigs had a monitoring system. Does it? If it has a computer, does it actually control anything? I guess I need to reset it, if it does.

I've ordered a manual... I'm sure that will answer many questions I have, but this one was so odd I couldn't wait. :)

:cool:;)

[john8662]

THe '88 models used the light as you describe.

They do have a PCM onboard.

Depending on what model you have, 1/2 ton or 3/4 ton will depend on what the PCM does.

In 1/2 ton models the PCM controls both the EGR and the Transmission's TCC lockup.

J

[DmaxMaverick]

The 1988 year model was a gray area for the Suburbans. The trucks got a facelift, but the Burbs, Blazers (Jimmy's), and crewcabs were held back 'til 1991. The SES could also the the rear anti-lock brake system sounding off (not really ABS, but similar, and I don't remember if it was an option or standard in 88). If it is running and shifting well, it is either the EGR or RABS. Check the 8th digit of your VIN. If it's a C (should be), it has EGR. 1/2 tons and LD 3/4 tons (IIRC, included 2500 V/R Burbs in 88) got the C engine. The "early" EGR engines worked well with the EGR because is was pretty simple in operation. Only open at idle (off pedal). But, higher mileage engines saw no benefit from using the EGR, and is actually counter-EPA. Costly to repair, and still didn't do much in regards to keeping green. The system could also include the passenger side exhaust pressure valve (like on gassers) that fail and trigger the SES.

Ultimately, if everything (but the EGR) works, it's best to defeat it (the EGR valve and exhaust restrictor) and move on. The PCM had no form of "limp mode", so it won't effect driveability. If you are subject to inspection, and they inspect for it, you'll have to repair it or "dummy it". Some inspection stations pull the air cleaner cover and check for the parts.

I don't normally advocate modifying any mandated system, but in this case, the older system on higher mileage vehicles is less "green" than w/o it. If you develop a conscience over it, lately it seems PC to just get a "carbon offset" and smoke on down the road. If it's good enough for them, it should be fair all the way around. I'm kidding, of course, but they can rationalize a tuna sandwich if you throw enough special interest tax money at it.

[FEF]

While investigating my defroster issue (no workie), I found my vacume pump appears to not work. I pulled the hose, put my thumb over it, and it didn't appear to suck.

As I found there's 2 wires attached to it, I can only assume it's to monitor the vacume pump. Since the vacume pump drives the EGR circuit, that may be something too.

Interesting rig, for sure.

[john8662]

The two wires are actually for engine rpm for the pcm.

Getting the vacuum pump pod/stem that has that sensor installed isn't common or inexpensive.

Workaround?

Yep, what I ended up doing on my '91.

Just replaced the pod, not the stalk. I removed the entire vacuum pump from the engine (pod/stem) and got it on the bench. I then took a new (well almost new for me) vacuum pump pod and installed it onto the old stem with the sensor.

The kicker is you gotta remove the vacuum inlet fitting from BOTH vacuum pods, you'll need the short radius 90* tube off your 88's pod to fit in your new pod. It's a press in thing, be carefull not to bugger it up, they're in tight, but not too tight, just work side to side until it comes out.

No vacuum is likely to be the reason for the code.

J