Ok, i have been getting 11mpg for months now. Took my car to the chevy dealer after resetting my ECU of all codes. They scanned it, and said it pulled a code 33, and 45. (same as what came up before for me, MAF(33) RICH EXHAUST(45)

I just bought a new MAF, and disconnected the negative cable for 15 mins to reset the ecu, and now it flashes a code 34?

What is a code 34? My crappy manuel says it's a vaccume sensor? Do our cars even have one of those? I might have a leak actually, but this is the first ive seen of that code.

What could be causing this? Is a code 34 not what the manual says?

After replacing my old MAF with the new one, It revved up to 2,000 Rpm, then dropped off then died. Then when I started it again, it whipped up and down the rpm's (750-2,000) back and forth a few times, sounded like it was stumbling really bad, then died again.

The burnoff relay looks like it's in good condition, it has all it's wires solidly in place. I haven't replaced it.

Please, anyone have any idea what's going on?

(Note to vader, I have replaced my prom with the updated prom a while back. I read an article you wrote months ago and bought the replacement, just to make sure this wasn't the problem. I replaced my MAF before, about a half year ago, and it made my car run worse, so i took it back. Haven't thrown the MAF code after i reinstalled the old one until i took it to the dealer and had them scan it again abotu a week ago. I throw both codes with the old MAF again now, and with the new MAF, just a code 34)

Any ideas anyone?

Thanks guys!

 

iwas having similar probs a while back and it turned out to be the MAS burnoff relay mounted at the firewall drivers side.

i think you should also check your TPS settings as i think this could cause MAS to act screwy .

im new at all this but reading all i can and picking up on things .
but anyways this worked for me .

hope i could help you!!

 

Code 33 tests.

First check air ducts for cracks, holes and tighten clamps.

With the ignition off, unplug the MAF and apply power to ALDL terminal
"G". Check the red wire on the MAF connector for power. If no power,
verify 12v on relay connector orange and white/tan wires. Verify the
connector black/white wire is grounded. Verify black wire from MAF
connector terminal B to ECM connector A11 with an ohm meter. Verify
red wire from relay connector to MAF connector with an ohm meter.
If all is good replace MAF power relay.

Turn ignition on, Check MAF connector dark blue wire for 12v, if so,
unplug MAF burn off relay and check again. If so, check relay
connector black wire for ground. If so, the black wire is shorted to
ground or the ECM is bad. If not, replace MAF burn off relay.


If the dark blue wire at the start of the above test had no voltage,
check the MAF connector dark green wire with ignition on for a 5v
reference signal. If so, and all connectors are good, replace MAF.
If no 5v reference on dark green wire, verify it from the MAF connector
to ECM connector B12 with an ohm meter. If the wire is good replace the
ECM. If the dark green wire has 12v on it, turn ignition off and unplug
the ECM connectors. Turn ignition back on and check again, if so,
it is shorted to power somewhere. If not, and all connectors and
grounds are good replace ECM.

This test will also repair code 34

 

Woah, thanks for the reply. I will have to set aside a lot of time this weekend, and give all of that a try.

My biggest question is why a new maf causes these problems, but the old one doesn't? Do i have like this special magic stock maf or something? haha

 

Thanks for the TPS suggestion too. I had my throttle body off last night too, so i did check and set it again once it was on.

 

The TPS can not set code 33. It is not in the MAF circuit or any
related circuits.

Don't worry about the new MAF, there are times when I get one
or two bad electrical items in a row before I get a good one
usually from one parts house but I won't mention their name.

 

Yeah, my first replacement was 250.00, and it looked like the stock maf. This one looks like the wells unit a bit. No wires, just a ISA looking card, with a funky shaped heat sink on it. it was 199. Borg warner.

 

Bad MPG A LOT of times has to do with the oxygen sensor...... Id fix that, and put in a new maf burn off relay and maf power relay and a fuel pump relay just for the hell of it total would only be about $50....

 

Called chevy, they had two part numbers under "Maf Relay". One was 17 bucks, the other 11. I ordered both. I figure one is power, one is burnoff?

I do have a new O2 sensor actually. Thanks for the suggestion though! I spent 1,400 on a 'tune up', which included everything, even a new cat. So i shouldn't be too bad off there.

 

The MAF power relay and the burn-off relay are the same. Not sure why you got 2 part numbers. The $11 part is #14089936. Try just swapping the relays first, and see if your code swaps, IE 33 to 34. Then replace the bad relay.

 

Still waiting on new relays. Does anyone have a diagram of what order the wires are supposed to be for the relays? Right now, the wires look awful, some are barely in the relay (stuffed them back in the old relays for now, but still having problems)

Also, I checked some things above on the maf connector itself, and it looks like my blue wire shows .004 volts with acc/on. and .025 volts with the ignition on. That is a bad burn relay right?

Red showed 14+ volts with the ignition on, and nothing with it off. Green showed .495 volts with acc/on.

I did not run power to aldl "g" for any of these tests though. no access to wire to run from my battery to the aldl connector.

Ill post back once i have the new relays in, a few days from now. I just wondered if anyone had a picture, or if they could tell me the order in which the wires go (i.e. yellow, green, black, black-white stripe, brown for burnoff) or something like that. I just want to make sure they are all in the right spot.

Thanks for the replies everyone!

 

When you shut the car off after it has been running for a while
the ECM grounds the black wire on the burn off relay connector.
This sends current to the dark blue wire to the MAF and starts
the burn off function of the MAF. The trace reading you got from
it is current back feeding from the MAF, this is normal. I would say
your burn off relay is good, don't relace it.

The red wire having power with the ignition on means the MAF
power relay is good, don't replace it.

You say the dark green wire shows .495, do you mean 4.95?
The ECM sends 5v on this wire to the AFM, if it is at .495 the ECM
is bad. It should read somewhere between 4v and 6v. If it is at
.495 you just found your problem, replace the computer.

As for relay wiring, on the burn off relay, terminal D and E are
orange, they both go to the +battery, hot at all times, fuel pump
relay terminal E, oil pressure switch, MAF power relay terminal A,
and ECM terminals B1 and C16. Terminal F is the black wire
(ground signal from the ECM terminal D12). Terminal A is the dark
blue wire, goes to terminal D on the MAF and to terminal C on the
MAF power relay.

For the MAF power relay, terminal D is the tan/white wire, it goes
to ECM terminal B2, fuel pump relay terminal A, the fuel pump and
to the oil pressure switch. Terminal F is the black/white wire, it
goes to ECM connector A12 and bolted to chassis ground.
Terminal E is the red wire and goes to the MAF terminal E.
Terminal C is the dark blue wire, it goes to the burn off relay
terminal A and the MAF terminal D. Terminal A is the orange wire,
it goes to the oil pressure switch, terminals E and F on the burn
off relay, terminal E on the fuel pump relay, ECM terminals
B1 and C16, and to +battery hot at all times.

 

Thanks again for a totally detailed responce!

No, i typoed, it was 4.95.

Well, I have the relays on order, it's 30 bucks, so i don't mind too much really. I figure it can't hurt anything.

I have had the ECU replaced once, a while back, but symptoms were even odder then these ones. Come to think of it, they were a bit similar to what my car acts like with the new MAF in it. The old maf runs just fine. Well, not just fine, rich as hell, but I just don't get it. It's like the old maf is some magical maf which seems to like working with my car, at least not going nutso and throwing codes and running super odd.

So im going to replace the two relays, and try out the MAF once again. Should i just buy another ECU as a matter of course? I will still use my updated PROM though if a new ECU is what i need. (the prom was an official GM release). How much are ECU units? Are they expensive like MAFs? Do you think the relays/ecu could solve the problem either? Or should I just take this MAF back for a refund, then go to the chevy dealership, and spend whatever huge amount of money they want for a MAF there?

Thanks!

 

Do you have any mechanic freinds to get access to a Snap-On
scanner? If so, some readings will help out alot.

I have never encountered an unsolvable problem yet but without
a scanner to get live readings with, diagnosing over the net
could prove to be a formitable challenge.

 

I just went back and reread your origional post again and you say
the engine races up and down with the new MAF. That is usually
a computer problem. Did you replace the ECM with a new or
rebuilt unit?

Your car has a 1227156 ECM, try to get a used one from
a salvage yard. I have had alot of problems with rebuilts.
Go to www.car-part.com and use the search form and
select your state and see if there is one close to you. If not
there are a couple of yards here that have them if I don't.
But a scanner will shed more light on the problem.

What was your old PROM ID?
What PROM ID did you update to?
The 4 letters on the silver sticker?

 

Hey

I have a 1985 IROC Z Camaro with the 305 TPI LB9 engine. I was having the same problems with engine codes. All I did was take it in for a good tune up and everything was good. Have u tryed getting a tune up, Total tune up with new wires plugs the whole 9 yard. Try that and if that doesnt work then I dunno

http://camaroz28.cardomain.com/id/56424

 

Thanks for the reply!

I have spent 1,400 on a 'tune up' already actually.

Sparkplugs, shocks, struts, fuel injector service, new cap, wires, and catilitic converter.

Im pretty good to go on a tune up, and my problems have been the same before, and after the tuneup so far.

 

hey VADER has a nice picture of the relays that you need to replace and has them labeled in the picture......... Thats weird they gave you two different part number for the MAF relays, when i bought mine im 99% sure the maf relays were the same, and the fuel pump one was a little different???

 

Yeah, im confused too.

I found that sweet wiring diagram on the main page for my car, and checked my relays out. Looks like the one labeled, "Maf burn off" is the power relay, and the other relay which is blank is my burn off relay.

Now im having magor idle problems again, with the old MAF hooked up. It doesn't die, but it revves up to 1,500 all the time. I took off my TB to see if it was the IAC or what not, and replaced it, and double checked it to make sure it was 1 1/16" out. All gaskets were replaces, all new screws were used.

Gotta love it. Hehe wish i had the cash to drop in a 350, i would just install a new wire harness if the engine was out. ; ) solve some of my problems i bet!

Thanks for the posts guys! Ill keep you all posted on how things work after i have my new transmission installed monday, and i have my relays in. Hopefully someone can help me figure this stuff out. These posts have rocked so far!

 

I have to say it's the computer, the rpm's running up and down
like that is a faulty computer.

 

Arrgh. Well, now im throwing a code 22 too!

I was driving today with my old MAF, which i do on weekends to keep the battery charged up. Well, my engine light came on, and i was idling at 2,000. Finally, after driving about a mile, the code shut off, and my car started stumbling. Sounded like someone kept putting their hand over the TB, then pulling it away. Like a odd thumping noise, then it would drop real quick, almost die, then revv back up real high. Pulled my car forward too, during the surges. spooky stuff on the road!

I set my TPS a few days ago. Could this be a problem too? Or even could this be a problem with my injectors? I just blew 1,500 on a new transmission i need, so im not easily in a position to get other thigns fixed up. I hate to blow 2,000 on sensors and what not, and still be in the same boat. Any more clues? Anyone have symptoms like these before?

Thanks.

 

Woah, alright. I checked my TPS (middle wire) a few days ago when i put on my throttle body. It read .545 volts. I left it there.

Well, today, after throwing a code 22, I checked it again, and it was all over the place. Without moving it, it was at .9 volts, then went up about a volt in either direction, back and forth, jumping all over the place.

So im going to try and find a TPS somewhere tomorrow, and install it, and set it again. Kind of odd how it suddenly went out like that. Made my car start to revv up to 2,000-2,500, and then drop and almost die, then idle at about 1,000, then jump up high again. whee! fun fun.

Luckily i have a very understanding boss. This sucks, i was supposed to have a transmission installed tomorrow, but i guess i can't make the morning appointment....

 

The ECM is bad. Nothing can cause all these problems except
for the ECM. You are loosing the 5v reference voltage from the
ECM that goes to the sensors. When a sensor looses the 5v
reference voltage, the sensor signal returning to the ECM
(ie. MAF, TPS, etc.) drops to near zero and the sensor sets a
code. When the circuit board in the ECM starts to break down
one of the major signs is the idle racing up and down. And the
1227165 ECM is known for this problem.

Find a used ECM, not a rebuilt. I do not put much faith in rebuilts.

 

ECM? Ok. Chevy dealer said they had two part # for my ECU, which one do i have? I had a replacement once, so i don't want to pull it out to get the number, in case it was wrong to begin with.

Well, I bought a new TPS, and it fixed the 22 problem. I also swapped the burn-off relay with the power relay, and it flashed me a code 33, and 36? (don' t have any idea what a 36 is, my manuels didn't say) And when put back right again, i still flash a code 33. No 34 anymore though. Im still using my old MAF.

 

The two ECM numbers they have are 1227165 and 16198445.
They are the same computer, either one will work.

Your car came with a 1227165 from the factory.
But either one will work, they are interchangable.

I would try to get a used one, they are a heck of alot cheaper.

 

Again swapmaster, thank you for your help!

Ok, that's good to know.

I replaced my ECU once before, a few years ago. It solved some odd problems then too. I just don't know if i should get another used one in case it has similar problems. I was able to pull up the second ECM on gmpartsdirect.com, 150.00, plus a 100 core? I guess you send your old one back or something. Ill have to call the chevy dealership here and see what they charge...

 

Christos,

Before you replace anything, you need to do a little diagnosis first.

Test the 5VDC supply from the ECM. You can test it right at the TPS sensor across the 'A' and 'C' terminals, then test the 'C' terminal (gray wire) to a good engine ground. You should get 5.0 VDC +/-0.05 VDC in all cases. If the second reading is significantly different than the first, start inspecting engine and ECM ground connections. If neither reading yields a 5.0 VDC supply or the supply is out of range, check the connectors at the ECM.

Many times a "bad" ECM can be remedied by simply removing the connectors, cleaning the edge connections on the circuit card, and reinstalling the connectors. The wiping action of the connectors being unplugged and reconnected is often enough to re-establish a good connection. I'd hate to think how many times s a good ECM was replaced just because of the fifteen year old plug-in connections that were going bad. After reinstalling the connectors on a replacement ECM, the installer would find all the problems solved, and surely blame the ECM without even trying the connections first.

Another related and frightening thought - you could have a wiring harness problem. There ARE splices in factory ECM wiring harnesses, just soldered, insulated, and taped over with the rest of the harness. I was surprised when I first discovered these, then I asked others who had modified their stock harnesses and sure enough, they are spliced on all cars.

Another possibility is having an AC component in the vehicle electrical supply. A failing diode in the alternator will introduce an AC component onto the DC lines, wreaking havoc with all the voltage-sensitive devices. GM lists the tolerance for AC voltage (measured directly at the alternator output stud) at 2.0VAC MAX. Personally, anything more than half a volt is too much for my comfort.

You should also measure the source voltage at the MAF, between the 'E' (red wire) and 'A' (black/white wire) terminals. You should read +12.0 VDC at the 'E' terminal to ground or the 'A' or 'B' (black wire) terminal. There should be no voltage differential between the 'A' and 'B' terminals unless you have poor engine or ECM grounds.

You can also monitor the MAf signal output between the 'C' terminal (dark green wire) and 'B' terminal. At a 900 RPM idle the voltage should be relatively steady around 800mV.

Check those before you buy any more parts.

 

Thanks vader. I will do that, as best i can.
Im not the electrical person at all really, but I do have a digital volt-ohm meter, so hopefully I can figure stuff out.

I did test the blue wire on my MAF, and it read .495 volts.

Well, my car is having it's new transmission installed today, but i had to get a flexplate, and motor mounts, and u-joints for the mechanic to continue. Gotta love the "300 to install" then the "oh no! look at all of this broken stuff!" phonecall an hour latet. As always, ill requet the old parts, even though i could easily see them being mangled up just by that request, regardless of condition. (not that im bitter, just been burnt twice now throiugh mechanics, looks like a third is too)

Still, props to summit, because i was able to get the engine mounts for 1/3 of the price, and got some good polygraphite ones. As for the flexwheel, it was about 1/3 of the price too. Still gotta pay for the installation of both though. That, and i gotta be gouged on the u-joint prices too (116 +80 install). Summit didn't carry u-joints anymore.

So in other words, I might have to let this thread die for a while, im way over my head at this point with debt from this transmission, so im not going to be able to do too much when it comes to replacing relays, ecm(if needed) and so forth.

Im going to hurt, but i got a new MAF relay, and burn off relay coming in. Once my car is back ill check connections, and also replace these relays. From what I could tell, the wires looked to be in awful shape.

Thanks for the replies so far everyone! I will post in a few days once I have my car back and some time to check as much as i can figure out electrially.

 

Ok, got my car back. New transmission running right, i think the 2,000 stall was a bad idea though, for my stock 305. ; (

Anyhow, I replaced my MAF burnoff, and MAF power relays today, cleaned up the wires a bit, and made sure they were set in there good, and used a bit of electrial grease. I then reset the ECU, and drove about 7 miles. No codes have flashed yet!

Not sure if my gas mileage will increase, I hope so, that's why i did all of this in the first place, to see why im getting 11mpg, driving like a granny.

I just got a ALDL interfacing cable, and moved the pins around so it will interface with serial pin "E" on my ALDL. I have a 165 ecu? the 160 baud. Im going ot try and get winALDL up and running. Hopefully I can get this progam working this time, it might clear some things up.

Ill post again when i have more info. Thanks for the read!

 

Having new brake pads installed today. Couldn't get the wheels off, bastards torqued them to death last time I had my tires changed.

On the way to the shop, i floored it in OD to get past a light, and my SES came on again. Dropped the car off, and pulled a code 33 again. So i guess the relays didn't help me out. The RPMs would rise and fall back and forth when i let off the gas.

This i-s with the old MAF still. Should I get a stock replacment MAF from the dealer and see if the 3rd times the charm? Or should I replace the ECU or what? Im very close to my limit on credit already, so im not sure what I can afford to do at this point.

Thanks!

 

I just bought a reman computer for my '86 iroc at o'reilleys for about $70 (mechanics price though)

 

Thanks for the info! I got a new thread

https://www.thirdgen.org/techbb2/sho...4&goto=newpost

Mechanic forgot to put oil in my car, and are trying to not pay for a new engine/rebuild. This is on hold for now. ; (