Edit: SOLVED! In my case the coolant temperature sensor (code 15) is what caused the 33/34 codes. Replaced the sensor and car runs great and code free.


First nice day this year decided to try and tackle it. Last fall I started with MAF cleaner with no change.

Today I followed TP's flowchart for code 33. I hook up the fused jumper to the fuel pump and it runs, but it sounds like there is a hiss/whooshing at the engine almost as if it's leaking into the cylinder or something? But don't see or smell any gas. Is it supposed to sound like that? Continued the chart and test MAF harness E(red) to ground and no light. Test both the orange(red?) and tan wires at the relay and both light on. And then I got confused at "Probe blk wire to MAF term "B" with a test light to 12V". I tested both the solid black and black/white strip to the battery with no light. Is that the correct way?

Then I jumped into code 34. Cleared codes (ground disconnected from battery for at least 30 seconds) and ran until SES came up. Checked codes and both 33 and 34 still there. According to the 34 flow chart, how could there not be a code 12? Isn't that part of the diagnostic series? But because the code 33 was still there does that mean the MAF is still bad even though in testing 33 the chart says it's either open ground or bad relay.




EDIT: And now I'm all of a sudden wondering if the flow charts are different from year to year. I pulled the ones I used from other threads but they they weren't likely for an 89. Hmmm. Where can the flowcharts be found?

 

I'm just curious here , are you saying the code flash sequence doesn't start out with code 12 three times , and then followed by the rest of the codes , but instead just starts right out with code 33 (or 34) without first beginning with code 12 ?

If so , I don't believe that's proper , everything I've ever read says the sequence begins with 12 ....

 

My sequence starts with 12, as expected, but the 34 flow chart has a branch that has "No code 12" as a path. Which seems odd.

And now I'm all of a sudden wondering if the flow charts are different from year to year. I pulled the ones I used from other threads but they they weren't likely for an 89. Hmmm.

 

Minor update: I swapped out the fuel and burnoff relays with each other, as I've read others have done, and the code 33 went away. Repeated the code 34 flowchart, http://www.chevythunder.com/maf_code_34.htm, and ended up at the "No code 12" but I still had the 12 and 34 codes. And following the chart as if there was "no code 12" I have no dark green wire to check for short to ground in MAF signal wire. Suggestions?

 

I believe the difference is because those are diagrams for 8 cylinder cars , and your working on a 2.8 V6 . If you look at the wiring diagrams associated with that V8 diagnostic flow chart the 1989 one shows the MAF Burnoff Relay that your 2.8 V6 doesn't have , your only MAF relay being the MAF power relay located next to the radiator . (If you swapped a relay with what you thought was a MAF burnoff relay , it wasn't a burnoff relay but instead likely the radiator fan relay or perhaps the fuel pump relay if you swapped one from next to the brake booster) . With such differences in the systems V8 VS V6 I think you'd be better served to find a troubleshooting chart specifically for the V6 . Remember , the different engine type equipped cars have different relay locations , your relays next to the brake booster being the A/C cutout relay , the fuel pump relay , and the radiator fan relay . V8 cars do indeed have MAF relays in that location , hence the need for only using V6 specific information if a proper diagnosis is ever to be made .

Here is your 1989 2.8 V6 wiring diagram , with the MAF circuit shown having a single power relay only .....

 

Thanks for that chart. I have also found a flowchart for code 34 for a '88 2.8L. So I hope that is close enough. I'll give it a go tomorrow and check back in.

 

So I found the same wiring chart as you posted in my Chiltons, and it's wrong on wire colors. But I also found that, according to my Chiltons, that my engine compartment is set up like the 85-87 2.8L component locations. The code flow chart for 88 2.8L seems pretty spot on. Using my multimeter in the Continuity setting as the test light. Worked through things until I got to step 4. E(brown) and ground was closed but A(orange black) and ground were not. And this is where I'm scratching my head. If A just runs between the sensor and relay, how could it be closed to ground? As well both ends of A have continuity with itself. I really hope I'm doing something wrong as this doesn't seem to make sense.

 

Honestly , I think your chasing your tail with those charts . Unplug the MAF connector plug and with the key on is there 12 volts between terminals A and C on the plug ? If yes , and if all else is OK with the air induction (factory configuration , no rips in the rubber boot , clean air filter , etc) , then your MAF is bad despite you having tried to clean it with the spray . MAFs are a notorious failure item on these cars and sometimes if your buying so called "Remanufactured" MAFs you may need to exchange it a few times before you get one that actually works , yes , it really IS that bad . If you can afford it , a new MAF from a quality manufacturer will save a lot of head scratching VS dealing with cheap MAFs of dubious quality ....

 

It's a bit funny that I was trying to do the 'leg work' on diagnosing before coming in the with the same old 'code 34' problems. Just so many threads of people who did the sensor first and still had problems, figured it was worth the effort. As well, my time is 'free' but I generally need to get budgetary approval from the missus for any major-ish parts. But I do have 12v across A and C. So I'll update once I get a replacement MAF. Thanks to you all who've been trying to help.

 

I very much don't blame you , loading up the ol parts cannon is usually the most costly way to diagnose any problem , but in the case of the MAF there really is no other way (once MAF 12V power has been established) beyond swapping in a new one (remembering that the MAF has likely the most DOA failures of any new part bought for our cars) .

 

Installed a new old stock AC Delco MAF and still throwing a 34. It idles a little rough at ~800rpm and bogs heavily until ~1500rpm before running smooth. What's next in the old part/diagnosing canon?

EDIT: also, it's been throwing code 15 the whole time. I assume that it isn't related, but I'm getting the new coolant temp sensor tomorrow. I'll install it and report back.
EDIT the 2nd: Went through did wire jiggling and looking at various wire connections, cleared codes and and tested again. It stopped sending the 34 code, runs pretty smooth with only a slight hitch when hitting gas at idle, and idles at ~800rpm still, but now sends a 33 code again?!?

 

Hi Sean , Sadly , there is a very good possibility your new old stock MAF is also bad , It's not unheard of for folks to return a malfunctioning MAF only to have the retailer turn right around and sell that MAF to the next guy . Tell me , have you checked things like the air filter not being dirty and that all of the air induction components are present and not damaged ? Like specifically the rubber boot connecting to the throttle body having no rips ?

If your engine is in otherwise good condition and in good tune , yes indeed you may have to go through two or three MAFS , even new old stock ones , before you get one that actually works , I have personally been there and can totally relate to the frustration of finding a good MAF to actually work in the car .....

 

Replaced the air filter already and done a visual inspection of the various lines and air components. I'll be inspecting for vacuum leaks next. Is it worth bothering with remanufactured MAFs or just get new ones? Thinking about just getting one from each of the local different stores and cycling through. Or should I not bother with one store or another; Autozone, Advance Auto, Napa, O'Reilly?
​​​​​​​

 

https://www.thirdgen.org/forums/elec...ml#post6362545

The guy in this thread , John in Rhode Island , says he has some good used ones .

​​​​​​​ He is a trustworthy guy if you want to try a known good used one VS a new or remanufactured one (of perhaps dubious quality ?)

 

Thanks! I'd much rather have a known working one than play the buy/return game over and over.

 

I am beside myself with wonderment. Finally replaced the the coolant temperature sensor (code 15) and, with the original MAF installed, car now runs great and has no codes. I guess it's my own fault for putting it off, because it was a minor pain in the *** to replace, but like nowhere have I seen code 33/34 equated to a coolant temperature sensor. And unless the issue is all of a sudden intermittent, very happy to have her running good. Thanks to all for trying to help.