check engine and AT lights activate upon flooring the accelerator pedal

Extra Pedal( Corrected):

Green/Yellow=B+
White=1.0v
Black=0.0v
Yellow=5.0v
Grey=5.0v
Green/Gey=5.0v

Hello guys...I know I must be driving you crazy, this car is driving ME crazy. I really appreciate your time. I've been wondering about the neutral switch, could a faulty one create this issues through a signal to the PCM that sends the car into this "safety" mode? Just wondering...even though it still wouldn't explain the signal disparity in the APP.

danield wrote: Hi there Ben. Yes, I did the test at the APP. I actually went further, I found another pedal from a 2011 and measured that one as well, there's no difference in pedals that I can see but maybe its different. I'll post pictures.

Excellent, thank you! I hate to nag, but I need to understand this clearly.

At the harness:

Green/Yellow= B+
White= 11.7v
Black= 0.0v
Yellow= 5.0v
Grey= 0.0v
Green/Grey= 5.0v

These were taken with the APP disconnected?

At the APP (oem pedal):

Green/Yellow= B+
White= 1.1v
Black= 0.0v
Yellow= 5.0v
Grey= 0.0v
Green/Grey= 5.0v

These were taken with the APP plugged in?

Extra Pedal( Corrected):

Green/Yellow=B+
White=1.0v
Black=0.0v
Yellow=5.0v
Grey=5.0v
Green/Gey=5.0v

So you borrowed an APP from a 2011 and plugged it into your 2005? Or, were these readings taken from the 2011 vehicle?

My biggest issue is the 5V reading on the Yellow wire. I've double checked the diagram, and this is definitely supposed to be a sensor ground circuit. :huh: Your picture of the APP connector matches up with the pin positions on the diagram, so I believe it's right.



I don't believe it's chance that the 1AA circuit is shared with the MAF sensor. It's tempting to suggest grounding that circuit, but I think you'd be better off doing a couple more tests first. One, disconnect the MAF and recheck the yellow wire at the APP. Second, with the MAF and APP plugged in, check the brown/yellow wire at the MAF. Like the APP, it should be 0V.

Mr. Tyler, yes the readouts are as you understood, 1 disconnected, 2 connected. I did borrow a 2011 pedal and read it from the 2005. Since the 2011 is a 2nd gen Mazda 3, I found a 2006 model at the junkyard and used that pedal as well. It gave me 0% reading so the pedal seemed to have been faulty. So I'm not counting that reading. I will perform the test you suggest and come back with the reads.

Awesome, thanks for the clarification.

I think your 0V reading on the Grey wire is suspect, too, but I'm wondering if that's the result of the open ground on the yellow wire.

Hello Mr. Tyler, I did the testing and this are the results:

Yellow wire no longer reads 5.0v it now reads 00.2v with or without the MAF/IAT connected. The b/y wire at MAF/IAT harness reads 00.1v when back probed connected.

At the APP harness while MAF/IAT and pedal disconnected reads:

G/Y= B+
W= 11.9v
BK= 0.0v
Y= 0.0v
Grey= 0.0v
G= 5.0v

Interesting! So it seems like there's an intermittent open in the 1AA circuit, causing a lack of ground to the APP.

With the APP plugged in and 0V on the yellow wire, what are the readings on the other wires? Also, it'd be interesting to watch the yellow wire KOEO and KOER.

I bet that if you clear the codes with the yellow wire working correctly, they'll stay away, and the throttle will work correctly.

Ok, will do the tests and give you the readings.

Mr. Tyler, here are the readings:

KOEO:

G/Y= B+
W= 1.1v
Bk= 0.0v
Y= 0.2v
Grey= 0.0v
G= 5.0v

KOER:

G/Y= B+
W= 1.2v
Bk= 0.0v
Y= 0.2v
Grey= 0.5v
G=5.0v

For some reason the "Ambient air temperature" continues to read -40°c and the "Intake air temperature" sometimes it reads -40°c and sometimes 38 to 45°c, which is normal. The -40°c is puzzling since I'm in Puerto Rico. The MAF/IAT sensor is brand new from yesterday, I replaced another brand new one with this one just in case it was faulty.

Signal correlation between Accelerator Pedal Position D and E continue to be around 5% difference. It went to a 1.5% difference for about a minute, as soon as the DTC appeared the correlation between them went back to around 5%

Mr. Tyler, here's another one. I hooked a different scanner to the car and it registered code P2138 by itself. I'm going to include screenshots of the Freeze Frame data, temperature looks wrong here as well.

danield wrote: For some reason the "Ambient air temperature" continues to read -40°c and the "Intake air temperature" sometimes it reads -40°c and sometimes 38 to 45°c, which is normal. The -40°c is puzzling since I'm in Puerto Rico. The MAF/IAT sensor is brand new from yesterday, I replaced another brand new one with this one just in case it was faulty.

That's interesting, because the APP and the MAF/IAT share a sensor ground, according to the diagram. -40 represents 5V at the sensor signal wire, either due to an open signal wire or an open ground.

Thank you for getting those readings at the APP! .2V on the yellow is still a bit high, but definitely better than 5V. :lol: Would you mind trying something for me? Grab a jumper wire and go directly from B- to the yellow wire at the APP (with a backprobe in the connector). Clear the codes and see if the P2138 comes back.

No Mr. Tyler, THANK YOU for helping me. Let me get some lights going and I'll get to it.

I'm really hoping that it is a ground, for obvious financial reasons...but inside I'm hoping it's that APP, Lol... The thing is, my dad is an Automotive Technician, has been since 1965, he's very well respected in the automotive community. He's old school in his diagnostic methods and I trust his skills more than anyone's I've seen, especially with automatic transmissions, in which he specializes in. But he doesn't use scanning tools very well and the language barrier (he doesn't understand any other language but Spanish) has prevented him from taking advantage of all the information out there. Anyway, the first thing he says when he sees the car's problems is : "That's a ground, look no more" and he walks off never to deal with the car again. Obviously he's talking about a "body ground" connection and this seems like an APP, tps or other ground problem, but it could still be a GROUND!! Ha,ha,ha...if it's a ground I'm never gonna hear the end of that old school rant at the shop...Lol..Here's to us finding the problem with new technology and old school knowledge. :->

:lol: Take a break 'till tomorrow if you want! No rush.

Mr. Tyler, here's what happened. The data on the left is with KOER after I cleared the codes that showed up after our test. The data on the right is Freeze Frame with KOEO after codes came and with the Y to B jumper on.

Picture order wrong. The single Data Frame is from another test. The picture with two Freeze Frames in it is the one described in the last post.

Ah crap, same code came back? Ah well, worth a try anyway. :lol: Thanks for giving that a shot.

I did another test on the MAF/IAT to see if the IAT part of the sensor is faulty even though it is new. This are temperature readings.

*KOEO & MAF/IAT Connected:

IAT= 104°F
Ambient= 68°F

*KOEO & MAF/IAT Disconnected:

IAT= -40°F
Ambient= 68°F

---

*KOER & MAF/IAT Connected:

IAT= 93.20°F
Ambient= 53.60°F

*KOER & MAF/IAT Disconnected:

IAT= -40°F
Ambient= 53.60°F

---

This was another set of tests after car was shut off.

*KOEO & MAF/IAT Connected:

IAT= 100.40°F
Ambient= 91.40°F

*KOEO & MAF/IAT Disconnected:

IAT= -40°F
Ambient= 68°F