Need help diagnosing MAF trouble code...

[PonchoCatalina]

I have been trying to resolve two trouble codes on my 91 Loyale for a couple of days now without success. They are code 23 (air flow meter) and code 24 (air control valve). Right now I'm focusing on 23 (I'll post about 24 later if I get this one worked out!). I've followed the FSM procedure for checking voltages and resistance and this is what I found: 1. Resistance between body ground and terminal B is 2.2 ohms (must be less than 10 ohms) = okay; 2. Voltage from terminal R to body ground is 12.12 volts (must be more than 10 volts) = okay; 3. Voltage between terminal W and terminal B is 0.21 volts (should be between 0.1 and 0.5 volts) = okay; 4. Blowing air through the MAF increases voltage between terminal W and terminal B = okay. This MAF was installed brand new just before I bought the car in September. I'm not sure what to look at next since all the numbers seem to check out. I welcome any tips you guys might have to offer as this computerized car is driving me crazy. Thanks.

[mikeshoup]

If the MAF checks out good, the next thing that can be of trouble is wiring. You may get stuck having to run new wires from the MAF straight back to the ECU.

 

My EA81T is having MAF hissy fits. Running wires back to the ECU helped.

[skishop69]

Yeah, I agree. To verify, you'll have to run those same tests at the ECU connector. That'll tell you if there's a wiring issue. Also check the terminals on both ends to make sure they're not damaged. Wires are good for breaking off inside the insulation. Does this code set as soon as you start it, or does it take some driving to get it to set? And just because blowing air through it changes the voltage, doesn't necessarily mean it's good. If the ECU sees the voltage jump radically in comparison to other correlated sensors, it will set the code.

[Gloyale]

If there is any chance that the wire loom going to the MAF has gotten hot? If so I have seen the shielding on the wires melt through and contact the inner wires they are shielding. This causes a short to ground. If you have a pinout of the ecu connector you can test continuity. Disconnect the MAF and the ECU connectors and check that you get continuity from one end to the other on each wire. You'll need a long jumper to connect to the MAF end and bring it into the cabin where you can check ecu. check that there is not continuity between any of the wires and the wire that is for the shield. There is an intermediate connector under the passenger side kickpanel. If you have a short, use this connector to repeat test to isolate short to engine bay or under dash.

[PonchoCatalina]

Yeah, I agree. To verify, you'll have to run those same tests at the ECU connector. That'll tell you if there's a wiring issue. Also check the terminals on both ends to make sure they're not damaged. Wires are good for breaking off inside the insulation. Does this code set as soon as you start it, or does it take some driving to get it to set? And just because blowing air through it changes the voltage, doesn't necessarily mean it's good. If the ECU sees the voltage jump radically in comparison to other correlated sensors, it will set the code.

 

 

Thanks for the responses. I've got some good ideas now to try once it stops raining. To answer the question about when the code is setting, it is immediate - as soon as the ignition is turned on (no diagnostic connectors hooked up). Thanks again!