2014 Taurus P0113, p0103

Lesage Technician Dearborn Heights, Michigan Posted   Latest   Edited  
Case Study
Driveability
2014 Ford Taurus SEL 3.5L (8) 6-spd (6F35)
P0103, P0117 Runs Rough

Hi everyone. 

Vehicle came in driving in limp mode and no other codes. Slams into D or R very harshly. Suspected Maf right away. At idle FT are at 0%. MAF at 0g/s and 0 hz, IAT is at 5V and -40°. Swapped in 4 different MAFs from another shop but same result. PCM logged a history code p0104. 

Scanned the car 2 weeks ago when it was running ok and it had 1 misfire code but not present now. Customer mentioned that VTC codes were intermittent in the past weeks also, but are not present now. 

From the diagram it seems that the MAF generates it's own 5v signal and converts it to digital then sends via the MAF (Yel/Vio) wire to the PCM. If that's the case why would the return signal be needed? I don't see how the MAF and IAT (pk/gy wire) could share the same return signal (Blu wire). Can anyone shed light on the circuit design. 

Now the MAF circuit shows about 9V when back probed. The rtn sig. shows 8mV, the IAT shows about 6V, and the vpwr shows battery voltage. Tapped the TB for 5V and fed the 3 MAF/ IAT wires they all came down to 5V except the sig rtrn (Blu) wire which showed no change. The scanner wouldn't show anything either on any of those circuit. 

I unplugged the PCM and MAF connectors and made a series circuit between the MAF/IAT and the PCM using 2 piercing probes and a halogen bulbs. All 3 wires lit up the bulb. Back probing and lightly front probing eliminated the connectors when the bulb lit up again. So at this point I'm calling it a ba PCM. 

All insights are welcome. Thanks to all.

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John Owner/Technician
Mechanicsburg, Pennsylvania
John Default
 

The green wire comes from a hot in start and run FUSE so it should have battery voltage on it. The maf doesnt create 5v ref it changes the bat voltage into 5v internally. the Iat appears to a normal Iat so if its reading 5 or 0 its either broken or has a wire issue to or from the pcm. same with the maf reading 0. id look for ground on the sig return wire 41 and variable signals on the MAF 40 and…

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
 

Hello John And thank you for your reply. I still benefited from it .

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Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
 

Hi Lesage, it is not a return signal, but signal return — another way to say signal ground (the current from the voltage source will return through it). If all is well, the voltage should be 0 there. Something that could be useful to know — what are voltages coming from the PCM when the MAF is disconnected?

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
   

Hi Dmitriy, Thanks for replying. Yes I made a simple mistake about the "return signal". You'll noticed that I corrected it further down. I typed so much today because I posted on another site also and responded, you can imagine. However, you spotted something in my understanding and clarified something: "signal ground". Thank you for that. Ok, disconnected the voltage comes back down to about…

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Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
 

Each component may have its own ground, or the grounds may be tied together if engineers designed it to work that way. You report that IAT is at 6V with the sensor plugged in — this suggests bad ground to the sensor. If the wire itself provides good ground, is the sensor connector good? — could a terminal inside be loose/partially broken/not touching the sensor pins? I know you’ve checked the…

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
 

I certainly will double check. I'll take the connector apart tomorrow. The 12V feed is between the IAT and the sig grnd. Maybe the separation between them cracked. I did not mention it but once I probed the sig rtrn and got 11.98V and that was less than battery voltage at the time. I thought it was just a WTF moment. However, since it's sig grnd now, I think the pin might've partially found its…

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Stephen Educator
Bethel, Ohio
Stephen Default
 

Start back at the basics. Lets look at the IAT. This is a two wire circuit. With the scan tool hooked up look at the IAT temp reading in generic mode, not manufacturer mode. With the key on and the MAF connector plugged in read the temp. Now unplug the MAF connector. Your temp reading should change. Next use a jumper wire and jump between the IAT reference voltage and reference ground. The temp…

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
 

Absolutely no offense taken. Thanks very much for the knowledge. Yeah i finished auto classes in 2008 but the program was, at the time, so massively underfunded with program admin. teaching 6 out of 8 modules. No teachers in the field providing supervision, no practice on an actual car unless you brought your own- even though there were donor cars from VW and Chrysler. Old text book…

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Gail Technician
Garner, North Carolina
Gail Default
   

Check the wiring harness where it crosses the transmission. Also try unplugging the trans range switch. See if the scanner readings change. This guy is the one to follow. He has a website too. aeswave​.​com/Engine-Perform…

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
 

Thank you Gail. Yeah I watch him on YouTube and even downloaded some content. I've meaning to get the book though. Thanks.

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John Owner/Technician
Mechanicsburg, Pennsylvania
John Default
 

Get the Ebook and or subscribe to his web site. The ebook has links to examples ( video ) of the issue , its testing and resolution. its great. Youre reading along as he explains something then there is a link to him diagnosing something using the technique he just trained. On his web site he has recorded all of his classroom lectures. scannerdanner​.​com is the best 11.00 per…

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Gail Technician
Garner, North Carolina
Gail Default
   

I have the ebook. Need to see if I can still access it. Ok. It still works.

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
 

I'll decide between the ebook and the hard copy. Thanks.

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Gail Technician
Garner, North Carolina
Gail Default
 

If you get the ebook make sure you save the activation code email.

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
 

Good tip. Thanks

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Stephen Educator
Bethel, Ohio
Stephen Default
 

I must apologize for my misunderstanding. Your right. If the ECM is not connected you can't hurt it. It takes time to learn this stuff and as I experienced, cash out of your pocket to attend classes. Good luck to you.

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

Stephen, The way he load tested the circuits wouldn't be able to cause damage to either the PCM or the MAF sensor. He disconnected the connectors from both the PCM and the MAF removing them from the circuits and then load tested the circuits which is the correct way to perform the test. I agree that performing a load test with the connectors attached to the hardware could or more likely…

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Stephen Educator
Bethel, Ohio
Stephen Default
 

Good. Just don't want to see it cause a problem. I may be wrong but it sound like this person may be a little new. I wish him the best. It takes time to learn electrical. But I'm sure he'll be fine. If he isn't a newbie and I sincerely apologize. good techs are hard to come by and even harder to develop.

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
 

You don't have to apologize at all. You are an educator and giving advice as so. I'm a newbie compared to the experts here. I remember the theory behind hot wire MAFs and how the ECU adjusts the current to the wire to maintain it's temp and interpret the difference in current according to the factory calibrated table as mass air flow/t, but diagnostics is a field all on its own nowadays. Dave…

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Stephen Educator
Bethel, Ohio
Stephen Default
   

Just make sure you don't have a signal ground problem internal to the MAF sensor​.​ Tell you what I'm going to do for you. I wrote a book that I think will help you out a bunch. It's titled OBDII Diagnostics Made Easy. This book was written for people like you. Without this becoming a plug for my book, I would like to send you a copy of it. E-mail me at … and I'll send you a…

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Helpful
Lesage Technician
Dearborn Heights, Michigan
Lesage Default
   

Hello and wow Stephen! That's very magnanimous of you. Thank you very much for everything. I'll gladly accept this present. Today, I took apart the MAF connector and everything was ok. Got a new MAF just for the unbelievable chance that all the other 5 MAFs were bad, but got the same result. Mounted a used PCM that has the same DG numbers and now the scanner is picking up MAF Hz and IAT temp…

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Stephen Educator
Bethel, Ohio
Stephen Default
 

E-mail me your shipping info to …. It will probably be Monday before I can ship it. Taking classes this weekend.

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John Owner/Technician
Mechanicsburg, Pennsylvania
John Default
 

Still watching this. Before I put a pcm in it id have to test for ground at the sgnrtn in the connector at the maf disconnected. Before i put a pcm in it id put a test light to power and touch that KOEO and KOER if it doesnt light id test that wire w the pcm disconnected for an open, then id put a pcm in it. Otherwise id try a 5th Maf from ford. I may have missed a step in your testing or even…

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
 

Hello and thanks John. I have done all that already, except for loading the sig rtrn wire while connected. Everything is in my posts. Some positives happened today. Plz refer to my reply to Stephen.

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Lesage Technician
Dearborn Heights, Michigan
Lesage Default
   

Hello everyone. PMI was successful with Autel 906bt. Parameter reset didn't work because IDS was needed to gain full access of BCM, so car didn't crank. Programming tech came over and did it over with the IDS and car cranked but no start.

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