Dreaded 33 Code
07-24-2017, 10:13 PM
#1
Dreaded 33 Code
I've been chasing a 33 code for too long it seems. It is on at all times. I have been following the flow chart in the FSM to determine where the problem might be. I've attached it below. When I get to step 4 I am seeing a negative voltage of -19.4mV and then -44mV when MAF burn off relay is disconnected. Is this possible? I am grounding black common to frame and probing MAF sensor connector with red probe. Continuing on if that is normal, I am wondering if there is a way to bypass digging the blue wire out of the harness to see if this is the actual problem. I've changed out both power and burn off relays and had to replace the connectors so I have access to wire connectors that can be redone. PO changed plug on MAF sensor. There is continuity on the entire 994 circuit. Does the "repair short to voltage" mean it is exposed somewhere and touching metal? Thanks and any other tips/ideas on the 33 would be greatly appreciated.
07-25-2017, 04:34 AM
#2
Race Director
The ECM has a "pullup" resistor on the MAF signal wire (you can see it in the second diagram to the right of the "B12" ECM pin label. If there is a loss of connectivity between the MAF and the ECM, that signal will go to 5 volts. When that happens the ECM sets an error code 33. It means that the connection between the MAF and ECM is not present. That could be caused by a corroded connector pin or a broken wire.
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86couper (07-25-2017)
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86couper (07-25-2017)
07-31-2017, 07:41 PM
#4
I checked the voltage at terminal C and it was 5.04 volts. I am using a newly purchased MAF sensor. I've inspected all wires and connections and they seem to be ok. I am not sure what to do now. Is there a way to check just the MAF sensor itself offline? Thanks.
08-01-2017, 04:32 PM
#5
Look at Step 5: This is correct for engine stopped, key ON.
Did you do the checks for A and B (grounds) as in step 4? Use a test light connect to +12Volts, and touch each terminal (MAF connector disconnected). The light should light for each.
I'd suggest do the flow chart again to be sure you didn't miss something, and if you get to 5 again with no problem found, you're at "Replace MAF". I don't know how to check a MAF other than installing it on another car that doesn't have Code 33.
Did you do the checks for A and B (grounds) as in step 4? Use a test light connect to +12Volts, and touch each terminal (MAF connector disconnected). The light should light for each.
I'd suggest do the flow chart again to be sure you didn't miss something, and if you get to 5 again with no problem found, you're at "Replace MAF". I don't know how to check a MAF other than installing it on another car that doesn't have Code 33.