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2015 Toyota Corolla
Model # NZE164
Engine # 1NZ-FE
Check engine light on, engine stalls sometimes.
Scanned ECU & found error code: MAF sensor circuit low
It's a 5-pin sensor (MAF & IAT)
Black wire - 12V MAF sensor supply
Green wire - MAF sensor signal wire?
Purple wire - MAF sensor ground wire?
Blue wire - 5V IAT sensor supply
Grey wire - IAT ground wire
(Wiring pin-outs based on my DMM probe)
Ran scan data & MAF sensor reading is 0.18g/s @ idle & it stays at 0.18g/s when the engine is revved up to WOT.
When sensor is disconnected, airflow reading changes to 0.20g/s.
With engine running, disconnected MAF sensor & engine did not stall.
With black DMM lead on battery ground, probed black & blue wire with red lead - got 13V & 4.95V
With red DMM lead on battery positive, probed green, purple & grey wire with black lead - got 13V (green/purple) & 3V. I know that I should get battery on IAT ground (grey) & MAF ground (green/purple). Is it possible that the circuit is a pull down type & therefore I am also getting 13V on MAF sensor signal wire? OR am do I have a short to ground?
What I didn't do was chuck a scope on the green/purple wire to check for a frequency/analogue signal.
Car is gone so I don't think I'll get it back in anytime soon...right now I'm leaning towards a new MAF sensor because if I had a short to ground then I wouldn't have got a subtle change in the MAF sensor reading, from 0.18g/s to 0.20g/s, when the plug was disconnected.
I have a 2008 Toyota Corolla, 1ZZ-FE engine, ZZE12* model.
I disconnected the MAF/IAT connector & grabbed a DMM for comparison readings.
Much the same as the 1NZ-FE sensor where MAF sensor ground wire reads battery, 12.22V, except MAF sensor signal wire reads 11.98V. I haven't identified the signal/ground wires using a pinout - I'm just assuming the 12.22V probe is ground because it's closer to battery voltage. Also note that DMM red lead is on battery +ve & black lead is used to probe connector.
Looks like a pull down circuit to me but the 0.24V reading difference (12.22 - 11.98) leads me to think that I should probably take a second look at the 1NZ-FE Corolla. When I DMM probed the 1NZ-FE MAF sensor ground & signal wire, they had equal readings of 13.12V. Perhaps the higher signal wire reading means that there is a less resistive path to ground - short to ground.
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