Intake Air Temp Sensor Issues

[Psychobot90]

I got the PO113 code with the rough, idle/lean condition and rough acceleration symptoms a few days ago. This came after changing my defective PCV which smoothed things out considerably. The code is accompanied by several misfire codes that change cylyinders at random (Mode6 shows random counts for each cylinder after every drive). New plugs, new coils, weephole, etc. already done. to solve the problem I bought the $15 sensor and installed it, but no dice. Same codes.
Research shows me that the charge air and coolant temp should be close, but Forscan shows:

Which is wayyy out of scope. Multimeter on the leads shows 5V reference is correct (based on battery negative), but the voltage going back to the ECM reads 33V which also out of range. Tested from battery negative to sensor wire.

This is driving me nuts...what am I doing wrong? I have a feeling the solution is obvious, but I can't see the forest through all the trees.

Here's some more Forscan data:

Iv'e been through this engine and I'm stumped here.

 

[jkayca]

I would double check the cable running from the IAT back to the ECM. Make sure you have a good connection. Do you get "reasonable" voltage values if you measure using a ground on the same wiring harness as the IAT? The fact that Forscan is showing different voltages makes me suspicious of the 33V you are seeing.

 

[Psychobot90]

I would double check the cable running from the IAT back to the ECM. Make sure you have a good connection. Do you get "reasonable" voltage values if you measure using a ground on the same wiring harness as the IAT? The fact that Forscan is showing different voltages makes me suspicious of the 33V you are seeing.

Good point. When I stop this evening I will test again using a ground in the same harness and report back.
If the numbers in Forscan are correct though I'm not sure what it's trying to tell me...

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[Psychobot90]

Good point. When I stop this evening I will test again using a ground in the same harness and report back.
If the numbers in Forscan are correct though I'm not sure what it's trying to tell me...

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Anyone have a diagram for the wiring loom that goes to the ECM? I'm looking for a ground wire and don't want to strip back too much of the jacket while I'm prodding around. Maybe a ground pinout number on the ECM connector?

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[Psychobot90]

I would double check the cable running from the IAT back to the ECM. Make sure you have a good connection. Do you get "reasonable" voltage values if you measure using a ground on the same wiring harness as the IAT? The fact that Forscan is showing different voltages makes me suspicious of the 33V you are seeing.

Ok, from what I've been able to find, the sensor sends voltage back to the ECM on the yellow wire. The voltage will spike if the sensor reads a low (cold) temp, and drop when it reads a high (hot) temp coming through the intake.
With Forscan showing -40° and my voltage reading of the sensor wire at 33V, this data seems to correlate.... Am I wrong? If that's the case and the sensor is reading -40°, what would cause that? Would a faulty ground create this?
I'd love to know which pin on the ECM is ground so I can test the sensor wire against it's own ground.

I'm really hoping to avoid taking this in for something that should be pretty simple to address. Any help would greatly be appreciated!

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[Psychobot90]

OK, I pulled ground off of the (obvious) ground leads coming from the loom at the firewall.
After starting it up this morning and letting it idle for 10 minutes, i get 20.9v on the sensor wire.
Forscan still shows -40 for the IAT. Again, ithink the voltage reading aligns with what Forscan is showing for temp, so I'm comfortable that it's an accurate voltage.
Now I just need to figure out the "why"!

 

[Yupster Dog]

@Elias Minaise ,
Does your outside temp work? What temp does it say? It very well could be your ambient air thermometer.

 

[Psychobot90]

@Yupster Dog Ambient temperature is at 73°. Forscan shows the same.

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[Yupster Dog]

@Elias Minaise
Worth a shot since you had not mentioned it.
You seem to have cleared a lot of other things it could be,
so what's left?
How about the plug for the IAT itself? you did say the new sensor acted the same as the old.

 

[Psychobot90]

@Yupster Dog I got a Doorman sensor from the parts store and it came with the new plug end so I spliced it on while waiting for the Ford part. Didn't resolve the issue. Code came back immediately on startup. Put the new sensor in and spliced on the original plug. No dice.

How about the other sensor on the turbo pipe? There is some confusion on my part on the differences between the IAT and Air Charge Temp Sensors... The one I bought was called Air Charge Temp sensor by ford, but the code is for the IAT bank 1 sensor 1. Forscan does not show a sensor for bank 2. Maybe I need to look at that other sensor? I can't remember the name of it, but it's on the turbo pipe below the fuel pump, driver side.

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[Psychobot90]

@Yupster Dog I got a Doorman sensor from the parts store and it came with the new plug end so I spliced it on while waiting for the Ford part. Didn't resolve the issue. Code came back immediately on startup. Put the new sensor in and spliced on the original plug. No dice.

How about the other sensor on the turbo pipe? There is some confusion on my part on the differences between the IAT and Air Charge Temp Sensors... The one I bought was called Air Charge Temp sensor by ford, but the code is for the IAT bank 1 sensor 1. Forscan does not show a sensor for bank 2. Maybe I need to look at that other sensor? I can't remember the name of it, but it's on the turbo pipe below the fuel pump, driver side.

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OK, here is the other sensor I was referring to (attached). It is labeled as "TCBP (Turbocharger Boost Pressure) / CACT (Charge Air Cooler Temperature) sensor" which is why I'm second-guessing myself now. Can anyone clarify whether my symptoms would be caused by this sensor failing?
It's worth noting that DTC now shows an underboost P0299 code as of this morning.

 

[Psychobot90]

Ok, new theory - could a bad PCM be the culprit?

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[Yupster Dog]

Ok, new theory - could a bad PCM be the culprit?

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As far as the PCM
you can multimeter at the posts to see if you get 5v that would clarify that question.

 

[Psychobot90]

As far as the PCM
you can multimeter at the posts to see if you get 5v that would clarify that question.

@Yupster Dog that would only apply to the reference wire though and we've already confirmed 5v at the sensor. It's the signal wire that is the wild card here, right? -40° I beleive is the max "bottom" range of the sensor, so I'm not sure if that tells us anything. I was thinking if the PCM was faulty, it could be interpreting the sensor incorrectly and causing the lean condition. Just a thought.

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[Psychobot90]

@LokiWolf do you have any input for me on this one?

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[Psychobot90]

For what it's worth, the oil temp is not showing any more. Am I crazy in thinking maybe the PCM is shot? With the p0113 and p0229 codes showing up at the same time, and now the oil temp gone, unless I'm mistaken all three of these sensors communicate directly to the PCM, right? Oh, and now it's showing the IAT code p0112. Could replacing the PCM be my magic fix? Any way to verify this?

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[LokiWolf]

For what it's worth, the oil temp is not showing any more. Am I crazy in thinking maybe the PCM is shot? With the p0113 and p0229 codes showing up at the same time, and now the oil temp gone, unless I'm mistaken all three of these sensors communicate directly to the PCM, right? Oh, and now it's showing the IAT code p0112. Could replacing the PCM be my magic fix? Any way to verify this?

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Man, It is either the PCM, or a bad ground to the PCM possibly.

First let’s Clear the KAM so the PCM will relearn. Connect all sensors back up before you do. There are several big plugs going into the PCM, I believe 3 on the 15-17. Disconnect them all. Turn on the headlights. Leave the battery connected. After about 15-20 minutes turn headlight switch off, reconnect all 3 plugs, give it a few then start it back up. Take it for a drive and then check sensor readings.


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[Psychobot90]

Man, It is either the PCM, or a bad ground to the PCM possibly.

First let’s Clear the KAM so the PCM will relearn. Connect all sensors back up before you do. There are several big plugs going into the PCM, I believe 3 on the 15-17. Disconnect them all. Turn on the headlights. Leave the battery connected. After about 15-20 minutes turn headlight switch off, reconnect all 3 plugs, give it a few then start it back up. Take it for a drive and then check sensor readings.


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I did a KAM reset and then PCM reset through Forscan - both back when I just had the p0113 code though. I'll redo in the morning after clearing the DTC and see what happens.

Only other thing I haven't done yet is replace the factory IAT connector. It's on order and I'll install as soon as I get it just to rule that out, but the existing doesn't show any defects.

For my own knowledge, am I right in thinking these DTCs are all related? No other issues prior to the IAT. Could a bad IAT/IAT wiring cause this chain of sensor malfunctions?

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[LokiWolf]

I did a KAM reset and then PCM reset through Forscan - both back when I just had the p0113 code though. I'll redo in the morning after clearing the DTC and see what happens.

Only other thing I haven't done yet is replace the factory IAT connector. It's on order and I'll install as soon as I get it just to rule that out, but the existing doesn't show any defects.

For my own knowledge, am I right in thinking these DTCs are all related? No other issues prior to the IAT. Could a bad IAT/IAT wiring cause this chain of sensor malfunctions?

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I think you have a common denominator. The root has still not been determined. Do it via the Plugs, not via FORSCAN.

I think it could if they share a common harness.


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[Psychobot90]

SOLVED.
I received the new Motorcraft connector, spliced it on and problem solved. Reset the DTC and all codes gone. Engine running smooth after an 800 mile trip with the travel trailer.

I decided to investigate the original connector and found that the reference wire was broken inside it's jacket. I found a little white stretch mark so i pulled on the wire and sure enough, it stretched. I spliced it all back together (I was still waiting for the replacement connector at the time), reinstalled it and my problems disappeared.

Now we know - if this sensor/connector is defective you can expect multiple DTCs indicating turbo underboost and/or misfires. The engine oil temp readings will also disappear from the driver display. It's worth noting that the -40° I was seeing for air temp is actually where the sensor signal bottoms out. I beleive it tops out in the other direction at 280°. I got both readings at different times.

I'm attaching a couple photos for the historic record.
Thanks for the input guys!

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