Code 33 here to stay?
Thread Starter
Junior Member
Joined: Dec 2004
Posts: 13
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From: wichita, kansas
Car: 85 MCSS
Engine: 305 TPI
Transmission: 2004r
Code 33 here to stay?
Try this out after you get the code 33 again.
1)Ignition off, Jumper ALDL terminal “G” to 12 volts using a fused jumper, Disconnect MAF Sensor, Probe harness terminal “E” (Ckt. 993) with a test light to ground.
Is the test light “ON” or “OFF”.
1a) “OFF”, Disconnect MAF power relay, probe (Ckts. 340 & 120) with a test light to Ground.
Light “OFF” on one or both, repair open in circuit that did not light.
Light “ON” both, probe (Ckt. 450) with a test light to 12 volts.
Light “OFF”, Repair open ground circuit.
Light “ON”, (Ckt. 993) open or faulty MAF Power Relay.
1b)“ON”, Remove jumper from ALDL connector, probe MAF sensor harness terminals “A” & “B” (Ckt. 450) with a test light connected to 12 volts.
Light “OFF” on one or both, Repair open in ground circuit that did not light.
2)Light “ON” both, Ignition “ON”, probe harness Terminal “D” (Ckt. 994) with a
Voltmeter, should read 0 volts. OK or Not OK
2a)Not OK, Disconnect MAF Sensor Burn-Off Relay, repeat test.
Not OK (Voltage Present), repair short to voltage in (Ckt. 994) from relay to MAF sensor or faulty MAF Power Relay.
OK (No Voltage), Probe relay harness (Ckt. 900) with a test light to 12 volts.
Light “OFF”, Faulty MAF sensor Burn-off Relay.
Light “ON”, (Ckt. 900) shorted to ground or Faulty ECM.
2b)OK, Ignition “ON”, Engine stopped, connect a voltmeter between harness terminal “C” (Ckt. 998) and chassis ground, should read between 4-6 volts. OK or Not
OK, Check all related connector terminals for making good contact, If OK, It is a faulty MAF sensor.
Not OK, (Over 6 volts), Ignition “OFF”, disconnect ECM A-B connector, Ignition “ON” repeat test.
Over 6 volts, repair short to Voltage in (Ckt. 998)
Less than 6 Volts, Check related Conn. Terminals and ECM ground Circuits, If OK, replace ECM.
Not OK, (Less than 4 volts), check for open (Ckt. 998), if circuit is not open,
It is a faulty ECM connection or ECM.
1)Ignition off, Jumper ALDL terminal “G” to 12 volts using a fused jumper, Disconnect MAF Sensor, Probe harness terminal “E” (Ckt. 993) with a test light to ground.
Is the test light “ON” or “OFF”.
1a) “OFF”, Disconnect MAF power relay, probe (Ckts. 340 & 120) with a test light to Ground.
Light “OFF” on one or both, repair open in circuit that did not light.
Light “ON” both, probe (Ckt. 450) with a test light to 12 volts.
Light “OFF”, Repair open ground circuit.
Light “ON”, (Ckt. 993) open or faulty MAF Power Relay.
1b)“ON”, Remove jumper from ALDL connector, probe MAF sensor harness terminals “A” & “B” (Ckt. 450) with a test light connected to 12 volts.
Light “OFF” on one or both, Repair open in ground circuit that did not light.
2)Light “ON” both, Ignition “ON”, probe harness Terminal “D” (Ckt. 994) with a
Voltmeter, should read 0 volts. OK or Not OK
2a)Not OK, Disconnect MAF Sensor Burn-Off Relay, repeat test.
Not OK (Voltage Present), repair short to voltage in (Ckt. 994) from relay to MAF sensor or faulty MAF Power Relay.
OK (No Voltage), Probe relay harness (Ckt. 900) with a test light to 12 volts.
Light “OFF”, Faulty MAF sensor Burn-off Relay.
Light “ON”, (Ckt. 900) shorted to ground or Faulty ECM.
2b)OK, Ignition “ON”, Engine stopped, connect a voltmeter between harness terminal “C” (Ckt. 998) and chassis ground, should read between 4-6 volts. OK or Not
OK, Check all related connector terminals for making good contact, If OK, It is a faulty MAF sensor.
Not OK, (Over 6 volts), Ignition “OFF”, disconnect ECM A-B connector, Ignition “ON” repeat test.
Over 6 volts, repair short to Voltage in (Ckt. 998)
Less than 6 Volts, Check related Conn. Terminals and ECM ground Circuits, If OK, replace ECM.
Not OK, (Less than 4 volts), check for open (Ckt. 998), if circuit is not open,
It is a faulty ECM connection or ECM.
(1) tested Terminal "E" and test light was on, move to (1b)
(1b) both "A" and "B" ON, move to (2)
(2) terminal "D" reads at 0 volts, move to (2b)
(2B) terminal "C" reads at 5.05 volts, check all connections
Everything checks out, I found a lose connection at the MAF Relay, repaired. Still had Code 33.
So I bought a new MAF, unhooked battery while I went into the parts store to get new MAF, replaced, hooked battery up. Check engine was back on within 5 seconds of starting the car. he car has nothing off the line. Once I hit 1500 - 2000 RPM it will take off and then run fine.
Hope I explained that right. What else would cause a Code 33
Thread Starter
Junior Member
Joined: Dec 2004
Posts: 13
Likes: 0
From: wichita, kansas
Car: 85 MCSS
Engine: 305 TPI
Transmission: 2004r
Well, though no one as answered, I think I have found the solution to the Code 33. After following the procedures outlined above and also the Prodedures listed in a TPI Tuning guide I found on this site from Hot Rod magazine, the car is running great. The only solution for the Code 33 if none of the above solutions work, you will need to burn a new chip with "higher" values for the MAF, I guess the Code 33 is thrown because the ECM sees more than 45 g, with the trottle less than 25% and less than 2000rpm. As far as I have found from searches, burning your own chip is the best way to get rid of the Code.
HTH
HTH
Member
Joined: Oct 2001
Posts: 401
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From: Seattle
Car: Which one?
Engine: 355
Transmission: 465
Did you do the test twice, per those instructions each time?
I had code 33, first time I came back with bad ECM, tested again, making sure I did it exactly as directed, and came back with bad MAF. Tested third time, bad MAF. Problem was bad MAF.
I read all the code 33 posts too, and there was some definite solutions with the PROM editing, but in many cases, I don't see WHY that would work...the gms/sec threshold for throwing that code is pretty high, at least for idle, and my engine uses nowhere near that limit. Engine RPM is also tied into that too, so it's possible the gms/sec based on a higher engine RPM (as opposed to just idle) can trigger it.
edit: to clarify, my code 33 would set immediately after clearing it and restarting the engine. It was 100% consistent. If it isn't a consistent problem, it's 10 times harder to accurately diagnose.
I had code 33, first time I came back with bad ECM, tested again, making sure I did it exactly as directed, and came back with bad MAF. Tested third time, bad MAF. Problem was bad MAF.
I read all the code 33 posts too, and there was some definite solutions with the PROM editing, but in many cases, I don't see WHY that would work...the gms/sec threshold for throwing that code is pretty high, at least for idle, and my engine uses nowhere near that limit. Engine RPM is also tied into that too, so it's possible the gms/sec based on a higher engine RPM (as opposed to just idle) can trigger it.
edit: to clarify, my code 33 would set immediately after clearing it and restarting the engine. It was 100% consistent. If it isn't a consistent problem, it's 10 times harder to accurately diagnose.
Last edited by dyeager535; Apr 25, 2005 at 03:11 PM.
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Joined: Aug 2001
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From: New york
Car: 87 IROC Z "ZZ4"
Engine: 350 "ZZ4"
Transmission: ck performance th400 3000 stall
Axle/Gears: 3:73 10 bolt
i have ben getting a code 33 with an aftermaket MAF a buddy got for me i think it was micro tech (had a chip inside of it) cause the filiment in mine was broke. and it was stalling when put in gear and running rich with the micro tech one
after going crazy i decided to put in the old broken bosch on just to see and i came up with code 34 but no stalling on me so i narrowed it down to both MAF were broke
after going crazy i decided to put in the old broken bosch on just to see and i came up with code 34 but no stalling on me so i narrowed it down to both MAF were broke
Last edited by Bobbyz; Apr 26, 2005 at 12:21 AM.
Senior Member
Joined: Mar 2005
Posts: 519
Likes: 2
MAF
I was having similar problems with my 88 Iroc, I was having code 34, car stalling and stumbling. I ran through the diagnostic tests as described above also. At first it pointed right to the MAF. After a couple days I decided to run through the test again, and again, and again. Somtimes the car would go an entire day without resetting the code, other times I could not get out of the driveway before it set. Very frustrating. I also found a loose connection at the MAF power relay, but this did not affect the code. I was about ready to purchase a $300 MAF when I decided to just throw in an MAF power relay for the heck of it, it was only $10 and worth a shot since the diagnostic tests were inconclusive. Sure enough, that was over a month ago and a couple thousand miles later, no more codes, runs great. I guess the relay was intermittent which was messing with me while diagnosing the problem, it had a mind of its own I guess. I also got alot of e-mails from people on here telling me how durable the MAF sensors are on these cars, and that the relays are usually the culprit. One fellow on here told me he had over 200,000 miles on his MAF without screens and it had survived several years of 10 second nitrous assisted drag strip passes. I looked at mine closely and the wire was not broken and looked fine. All this convinced me to just try the relay for 10 bucks. I am glad I did.
Just my experience. Hope that helps, Larry.
Just my experience. Hope that helps, Larry.
Thread Starter
Junior Member
Joined: Dec 2004
Posts: 13
Likes: 0
From: wichita, kansas
Car: 85 MCSS
Engine: 305 TPI
Transmission: 2004r
I got it finally, After following the steps I quoted above, I narrowed it down to a bad MAF. After replacing the MAF I apparently didnt clear the codes in the computer. So Today I double checked everything agian. Everything tested good so I unhooked the computer completely. All codes are gone now, I reset the IAC agian and its all good now. Thanks for the help guys.
Chris
Chris
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