1985 service engine code 33
Thread Starter
Pro
Joined: Aug 2004
Posts: 581
Likes: 0
From: Charlotte North Carolina
1985 service engine code 33
Before I buy an MAF sensor, would appreciate any input for the following problem.
Code 33 is set after the car sits for two days. Disconnect the battery to reset to ecm and all is well with the world, idles fine, power is fine, etc.
I've gone thru the Service manual code 33 diagnostics and keep coming up with, "check connections and if connections are ok, replace the MAF."
I'm getting all the proper voltage readings at the MAF connector and the burnoff module connector to the ecm.
Any thoughts appreciated.
Code 33 is set after the car sits for two days. Disconnect the battery to reset to ecm and all is well with the world, idles fine, power is fine, etc.
I've gone thru the Service manual code 33 diagnostics and keep coming up with, "check connections and if connections are ok, replace the MAF."
I'm getting all the proper voltage readings at the MAF connector and the burnoff module connector to the ecm.
Any thoughts appreciated.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by game on
Before I buy an MAF sensor, would appreciate any input for the following problem.
Code 33 is set after the car sits for two days. Disconnect the battery to reset to ecm and all is well with the world, idles fine, power is fine, etc.
I've gone thru the Service manual code 33 diagnostics and keep coming up with, "check connections and if connections are ok, replace the MAF."
I'm getting all the proper voltage readings at the MAF connector and the burnoff module connector to the ecm.
Any thoughts appreciated.
Code 33 is set after the car sits for two days. Disconnect the battery to reset to ecm and all is well with the world, idles fine, power is fine, etc.
I've gone thru the Service manual code 33 diagnostics and keep coming up with, "check connections and if connections are ok, replace the MAF."
I'm getting all the proper voltage readings at the MAF connector and the burnoff module connector to the ecm.
Any thoughts appreciated.
You can also try the tap test. With the engine idling, Tapethe bottom of the MAF with the handle of a screwdriver; if the engine stumbles the MAF is bad.
Hope this helps.
Jake
Instructor
Joined: Jan 2005
Posts: 141
Likes: 0
From: Tucson AZ
relay locations
on my '85 the maf burnoff relay is mounted on the wheel well inner just in front of the battery. The maf power relay is on the firewall just behind the battery. Don't know if that's stock, but there they are.
Says you should replace both relays when you replace a maf.
Says you should replace both relays when you replace a maf.
Thread Starter
Pro
Joined: Aug 2004
Posts: 581
Likes: 0
From: Charlotte North Carolina
Visually checked the maf wires and appears none broken.
If maf wires were broken, why would it run ok for 2 days and then not? One would think that if maf wires were broken/open, then it would never run ok.
Thanks for your input. Very frustrating problem to pin down!
If maf wires were broken, why would it run ok for 2 days and then not? One would think that if maf wires were broken/open, then it would never run ok.
Thanks for your input. Very frustrating problem to pin down!
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
I must be missing something, because one of our members says the 85 has only one relay and it's behind the dash.
I've got an 86 and it has two, mounted on the firewall behind the battery.
Color me confused.
Jake
I've got an 86 and it has two, mounted on the firewall behind the battery.
Color me confused.
Jake
Thread Starter
Pro
Joined: Aug 2004
Posts: 581
Likes: 0
From: Charlotte North Carolina
According to the GM service manual it is located right of the ecm on the passenger side. I pulled the connector and verified the wiring so I am confident that I had the burn off input to the maf.
The service manual does not reflect relays between the burn off and the maf. However, I do not hear the relay clicking from the dash that happened before this problem showed its ugly face.
Thanks for your input.
The service manual does not reflect relays between the burn off and the maf. However, I do not hear the relay clicking from the dash that happened before this problem showed its ugly face.
Thanks for your input.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by flylowguy
on my '85 the maf burnoff relay is mounted on the wheel well inner just in front of the battery. The maf power relay is on the firewall just behind the battery. Don't know if that's stock, but there they are.
Says you should replace both relays when you replace a maf.
Says you should replace both relays when you replace a maf.
So what did GM do, switch to the two relay setup late in 85?
Jake
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Thread Starter
Pro
Joined: Aug 2004
Posts: 581
Likes: 0
From: Charlotte North Carolina
Thanks for your input. According to the 85 service manual the realy is located inside the burnoff module. No other relays are shown on the wiring schematic of the service manual.
If the relay was not working, I would not see voltage from the burnoff module after shut down. However, I see the voltage for a couple of seconds at the burnoff connector to the ecm.
I think I will try the maf as the service manual test indicates.
If the relay was not working, I would not see voltage from the burnoff module after shut down. However, I see the voltage for a couple of seconds at the burnoff connector to the ecm.
I think I will try the maf as the service manual test indicates.
Thread Starter
Pro
Joined: Aug 2004
Posts: 581
Likes: 0
From: Charlotte North Carolina
Thanks for your input. I'll check behind the battery for the relay. Would be great if that is the problem because the maf cost $200 plus and the burnoff relay dealership retail cost is $900.00!!
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by game on
Visually checked the maf wires and appears none broken.
If maf wires were broken, why would it run ok for 2 days and then not? One would think that if maf wires were broken/open, then it would never run ok.
Thanks for your input. Very frustrating problem to pin down!
If maf wires were broken, why would it run ok for 2 days and then not? One would think that if maf wires were broken/open, then it would never run ok.
Thanks for your input. Very frustrating problem to pin down!
Your initial post ended with "Any thoughts. . ." To me that means just that, so I mentioned the things that you hadn't listed as being checked. As to "why", only clues I have is it could be heat or vibration related.
I've seen the tap test in a couple of mag articles and, I believe it's even in the 86 Vette Shop Manual.
So, you got the correct voltages on the burn-off test, but no longer hear the clicking sound that you use to hear. What does that tell you?
Jake
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by game on
Thanks for your input. I'll check behind the battery for the relay. Would be great if that is the problem because the maf cost $200 plus and the burnoff relay dealership retail cost is $900.00!!
I bought my last MAF at a wrecking yard about three years ago. $50.00 Many 'F' bodies use the same one. If I were you, I'd check for the relay there too
Jake
Thread Starter
Pro
Joined: Aug 2004
Posts: 581
Likes: 0
From: Charlotte North Carolina
Jake,
Don't know. Is there a relay inside the maf the caused the clicking or is there a relay located somewhere that the shop manual does not address as flylow suggests?
Thanks for your input.
Don't know. Is there a relay inside the maf the caused the clicking or is there a relay located somewhere that the shop manual does not address as flylow suggests?
Thanks for your input.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by game on
Jake,
Don't know. Is there a relay inside the maf the caused the clicking or is there a relay located somewhere that the shop manual does not address as flylow suggests?
Thanks for your input.
Don't know. Is there a relay inside the maf the caused the clicking or is there a relay located somewhere that the shop manual does not address as flylow suggests?
Thanks for your input.
My thought is that if you cannot hear the clicking sound that you use to hear before the problem started, but CANNOT hear it now, then it must be bad even though the voltages check out okay.
If the burn-off relay is working properly, you should be able to actually see the MAF wires glow when you shut down the engine. I've never actually checked mine, but I've read posts where others have checked theirs.
Hopefully guys with 85s or who have watched their burn-off function will post.
But $900, that's outrageous!!!!!!!!!!!!!
Jake
Racer
Joined: Dec 2003
Posts: 277
Likes: 3
Originally Posted by game on
Jake,
Don't know. Is there a relay inside the maf the caused the clicking or is there a relay located somewhere that the shop manual does not address as flylow suggests?
Thanks for your input.
Don't know. Is there a relay inside the maf the caused the clicking or is there a relay located somewhere that the shop manual does not address as flylow suggests?
Thanks for your input.
frank
Drifting
Joined: Sep 2004
Posts: 1,961
Likes: 2
From: Fort Knox
Originally Posted by frank j. moran
the burn off module on an 85 is behind the IP (bread box) on the right side. This module is expensive, however it is used on all F bodies in 85 with TPI. Are you sure it's bad, does the wire in the MAF sensor glow when you shut the engine down, if so it doing its job.
frank
frank
Im jackn' the thread for a minute, but let me get this right - I could turn off the engine, and while looking into the maf, actually see a glow from the wire? Thats cool as sh8T ... how long does the burn off last? Seems like thats the best test to see if your MAF is fubar.. Is that assuming too much?
thnx
snoopdan
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Although an 87 is different, my intermittent MAF problem was easily
solved by replacing the MAF burn off relay and power relay (both)
for less than $20. If I were you I'd be locating and replacing your
relay(s).As to location on an 85 I have no idea.
solved by replacing the MAF burn off relay and power relay (both)
for less than $20. If I were you I'd be locating and replacing your
relay(s).As to location on an 85 I have no idea.
Team Owner
Joined: Sep 2001
Posts: 62,099
Likes: 1,724
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
85 has only one burnoff module inside the passenger dash near the ECM, it does NOT have 2 MAF relays on the firewall behind the battery. GM did not make a change midyear with the 85 either, they didnt do the 2 relays until 86.