Just thought maybe one of you guys might know why a code 33 is being set....

New MAF and relays.

When code is set the engine runs the same.

Used a scantool and looked at values but the code would not set while I was monitering it.

Only thing I can think of is that the engine is beathing out of the range for the air flow. I am using the xxx165 ECM, if I remeber right the prom is a 8201. I am not sure what the 8201 goes to.

Thanks,
Matthew

 

Check that the connector to the maf. I was getting a code 33 and I could not find the problem. After about 2 weeks of pulling my hair out I finally realised that the wires in the maf connector were pushed in too deep inside the connector to contact the maf.

 

Every 3 or 4 years my car throws the 33 code. I put a new relay in and it goes away.

 

I thought the prom was for a 305 and the 350 causing this to occur but I would think it would be set under similar conditions.... like at wot only or something.

 

Try pulling the fuse next to the battery to reset the computer.

 

L_MD,

The "8201" doesn't appear in any of my tables, but they aren't really that complete, either. Try to get more information from the EPROM foil label, liek the three letter code that precedes the numeric code.

If the PROM is indeed designed for a 305 MAF installation, the error will be impossible to prevent since hte ECM will expect a lower intake flow at any given RPM and TPS voltage. One way to "cheat" around the problem is to increase the TPS voltage to the upper end of the allowable range. Thsi will "fool" the ECM into thinking the throtle is more open, and that the additional air being metered is acceptable.

Another thing to recognize is that the original 1986 TPI programs had several defficiencies, including tight MAF tables that would set DTCs when everything was actually within acceptable limits. The best thing to do might be to burn a PROM for a $6E mask and use the 1989 ARAP code MAF tables, which seem to be the most accurate. That updated mask will work just fine in your 1227165 ECM. It does rather well in mine. Of course, when doing that, you might as well improve the fuel and spark tables, tweak the enrichments for your cam and transmission/gearing, and adjust teh fan, TCC, and other parameters to match your setup and desired driving style.

Short of that, get the complete PROM I.D. and we'll be able to tell if the MAF limits are correct for your 350.

 

I was looking at purchasing the equipment to burn new proms... but where do you find the files or mask's to burn on the new chip?

I am just afraid the the software for the burner will be something I cannot understand. Does it have a table with numbers or a dialog box that says "timing" (for example) and then you chancg the ranges?

I dont want to purchase the burner and find out I cant use it and then wish I paid a company(like TPIS) to burn a chip for me.

A guy I work with has an extra ecm for his 86 camaro... I was going to borrow his prom but it is different than what I have. It is a hypertech chip part number 127052. I've heard both bad and good things about the hypertech proms.

He has one in his camaro and loves it compared to the stock.

I will pull the cover on my ecm and see what the part number on it is. Hopefully you can cross reference it.

Thanks for the Help!
Keep it coming-

 

I just pulled the cover off my ecm, I guess I had a brain fart... the proms are not different.

There is a sticker on my prom that reads:
delco
abwt
8674

On the side of the prom the numbers are:
68767
8651

Let me know if these number mean anything to you!

 

I had the exact same problem!! Pin "C" (green wire) inside the connector was sliding back when connected to the MAF and making poor contact.

I believe the code 33 is set if the ECM sees over 45 grams/sec (or what ever value is burned onto your chip) of airflow with RPMs below 2000 rpm for over 30 sec or something like that.

(Don't quote me on the specific values that trigger the code 33, I'm going purely from memory here and I'm getting OLD!!!!)

Check the voltage from pin "A" to pin "C".
Pin "A" is ground.
Pin "C" gets 5 volts from the ECM.

During low airflow conditions, the MAF will decrease the resistance to ground for pin "C". The lowered resistance will pull down the voltage on pin "C" which the ECM sees as an indication of lower airflow.

As airflow increases, the resistance to ground (for pin "C") will decrease, so pin "C" voltage will climb higher and higher.

Look for a high voltage on the green maf wire with eng idling and while wiggling the MAF connector.

 

That PROM is for a 350, and the MAF high threshold is set at 45 g/S. That can be altered easily.

You can find much helpful information on the PROM board here, and many sites that have tuner/binary/mask file archives. Mark Mansur's TunerPro is a good package.

 

I tried the hyper tech prom.... the idle was low enough the car would not hardly run.

At wide open throttle it spark knocked so bad and black smoke rolled out the tail pipes.

It didnt take long before I pulled it back out!

**Vader**
Is the prom I have, one that can be reprogramed? Would I need to buy the tuner pro or the files I need?

Could you take a picture of the screen in the program and email it or attach it here?

lawrence_1md@yahoo.com


Thanks a bunch!

 

I was getting a code 33 all the time (within 5 seconds of starting rig) as well when I did my swap, and the factory code 33 troubleshooting flow chart proved it was the MAF.

I'm running a Vortec headed 355 on a 1987 305 PROM and my gm/sec are nowhere near enough to hit 45 at idle. No codes.

The code says gm/sec high, and posts on here said that raising the threshold solved the problem for some, but the MAF couldn't have been reading correctly if a new one solved the problem, at least in my case.

 

when I had the scantool at idle it was show about 10 grams per second... for the price I paid I hope its not that.

Since then I have moved almost 3 hrs from the store where I bought the maf sensor. It is still in warranty but the is not a store like it here.

 

Error code 33 is set when all of the following are true:
1) engine under 2000RPM,
2) over 45 g/sec seen by MAF, and
3) less than 25% throotle.....

The only way that I got rid of my 33 error code (after buying a new MAF, replacing all relays) was to get a custom chip burned for me and now I do my own.

Lawrence, if you can use an Excel spread sheet, then you can burn a chip.

 

So did/does your setup match all of the above criteria? From my winALDL scans, I see what the poster is, about 10 g/sec at idle, and that isn't enough to trigger a code at idle unless something else is wrong. (and yes, I was able to see it hit 60 g/sec under certain "mild" driving conditions, so I'm fairly certain it was reading right)

Not a computer programmer, but if a new chip solved your problem, then something in the PROM was the culprit, right?

 

the chip was not the cluprit, exactly, the GM programmers had the MAF limit for this condition set at 45 gms/sec in the chip. The chip was not faulty, but the decision about the 45 gms/sec was.

With an A4 car, and some mods (heads/cam/headers/etc) I would have these 3 conditions simutaneous when on the xway , tranny in 4th gear and at about 60mph. The MAF reading was just over 45 gms/sec,,, engine speed just under 2000 RPM,,, at part throotle, posible climbing a slight incline.

For a awhile I got around the issue by running the tranny in 'D' not 'OD', and after being at 70mph switch to OD.

I could, on purpose, set this 33 code any time I wanted to prove the point of the 3 conditions. BTW: I did not empirically come up with these 3 conditions. They are printed in my 1987 service manual.

my current '87 car has been geartly modded since those days, however.

 

Yes!

The code becomes present at low thottle position and under 2k rpm. But can never get it to do it the same time. Sometimes it will happen on decel, sometimes it will occur on cold starts...

I am going to get the scantool from work on friday... and then try to see if its going over the set limit.

 

L_MD,

Yes, the EPROM installed in your ECM is re-programmable, but it must be erased first via a UV light source. I find it easier to simply program a new PROM (less than $6 for a blank PROM), alter the carrier/CALPAK by adding a socket, and keep the original PROM for reference (or until you're certain you have a good copy of the binary code and will not need the original again). Installing a low-profile, gold contact socket (like an Augat) in the CALPAK allows you to change the PROM without damaging the CALPAK, allows the cover of the CALPAK to be installed as the original was, and makes for a very reliable device once assembled. You can get sockets for about the price of a PROM, so for $12-15 and a little soldering and effort, you can have a means to change your PROM as much as you like.



Another option is to buy or build a special converter board, like Craig Moates offers, that uses your original CALPAK as backup and replacement PROM as the primary program. You don't need to even open the cover of the CALPAK.