MAF sensor Chevy Colorado 2008 gone bad?

Thread Starter

Volttrekkie

Joined Jul 27, 2017
60
Hi. My engine all of a sudden started idling rough. It has less than 50k on it. I tried to test it but turns out that they fabricated the MAF sensor so that I cannot stick my multimeter probes into the back of the connector to measure while it is running. So, I did the best I could and here is what I found. There are 5 wires: Y, B/W, Pink, Black, LB. Y and B/W measure 5V. B/W and Pink measures 12V. Pink and Black measures 12V. Black and LB measured 5V. This is of course on the power side with the truck running. I take it Y and B/W is for the sensor. B and LB are for the Intake Air Temp sensor. Pink is for heating the hot wire. So, everything looked good on the power side. Then I did ohm readings on the sensor itself. Y and B/W was OL. And everything else was OL too. I probed around a lot. All OL. So, I think I need a new one?
Also, how does 12V and 5V share the same ground, B/W and Black? Wouldn't different voltages have different grounds? Or are they all some how using chassis ground as a 0V reference? But then how does 12V power flow from Pink to the negative terminal of the 12V battery?
 

JohnInTX

Joined Jun 26, 2012
3,804
Have you pulled the codes from the ODB-II connector under the dash? AutoZone and other outfits will do that for free. That might help you ID the problem. It could be a lot of things - MAF but also intake manifold gaskets, other vacuum leaks, fouled plug, fuel delivery issues, etc. Pull the codes and go from there.

Good luck!
 

Thread Starter

Volttrekkie

Joined Jul 27, 2017
60
Thanks. I will call Autozone tomorrow. I changed the spark plugs. Fuel filter is in the tank so I cannot change it. But it only has 47k miles. I heard no leaks.
 

Hymie

Joined Mar 30, 2018
708
I would recommend everyone who owns a vehicle with a compatible OBD port (virtually every car built in the last 20 years) has one of these:-

https://www.ebay.co.uk/itm/Universal-2017-D900-Scanner-Reader-OBD2-EOBD-Data-Fault-Code-CAN-Diagnostic-Tool/263628870206?epid=25007742790&hash=item3d6181523e:g:eWQAAOSwBCFall07&_udlo=15&_sop=15&_pgn=12&_sacat=0&_nkw=obd+scanner&_from=R40&rt=nc

It will pay for itself after one use. There are many different models available, but this one comes with a protective case so you can throw it in the trunk and forget about it until needed.
Many cheaper versions only display the fault code – leaving you to look up to code on a separate CD, whereas this one displays the code and fault.

Many garages will charge more than £17.99 to perform the scan and advise of the reported fault(s).
 
Got to this thread too late. Pull the connector to the MAF. Driveability might get better.

I had recently fixed my mom's Chevy and while she was driving it, it would not even idle. Since that was the last thing replaced a few days ago, i decided to pull the connector. Instantly, driveability improved.

Incidently, it was a sensor from Autozone. I drove it there; may have done a free code read and exchanged and replaced in the parking lot.
 

Thread Starter

Volttrekkie

Joined Jul 27, 2017
60
I ordered the new MAF sensor from partsgeek.com. On this one, pins 2 and 4 had continuity. The old one was OL. They must be the 2 grounds. All the other pins were OL. But pins 4 and 5 measured 1.2kohms. Maybe my meter is bad. How can it measure 1.2kohms in ohms mode but fail in the continuity mode?
I plugged it in. Idle was still rough. 750rpm. And the check engine light went on. I disconnected the battery and reconnected it. Same thing. Pins 4 and 5 measured 1.2volts. When I stepped on the gas pedal, it just stayed 1.2volts. Pins 1 and 2 were 5V. When I stepped on the gas pedal, it was still 5V. What am I doing wrong? I searched for a vacuum leak but could not find one. Only 47k miles. Is anybody familiar with the MAS sensor? I think I bought a bad part. Am returning it tomorrow.
 
I plugged it in. Idle was still rough. 750rpm.
Basically what happened to me, but it did work initially. The 750 RPM is just annoying. Disconnected, the car did MUCH better. It was at least driveable. Not 100%. If you bought at Autozone, return it to Autozone.

In general, you need 3 good drive cycles to reset a code. Autozone won;t reset codes, but you can generally borrow tools with a deposit. Then you can reset it. Disconnecting battery sometimes works. You can't generally pass inspection with just resetting codes. The car must do a drive cycle.

http://www.lyberty.com/car/drive-cycle.html
 

Thread Starter

Volttrekkie

Joined Jul 27, 2017
60
I returned the part to partsgeek.com. I think they sold me a bad part somebody returned. According to one blog, pin 1 should read 2.2 to 2.7 K Hertz at idle. It read 0. pins 1 and 2 are the mass air flow pins.
 

Thread Starter

Volttrekkie

Joined Jul 27, 2017
60
I fixed it! I bought a new part from Advanced Auto. $98. Ouch. But the check engine light is now off. Turns out pin 1 reads 2.5 K hertz at idle and responded very well to throttle but only if the negative lead on my multimeter is not connected. I just used the red lead only. How is this possible?
 
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