[iminhell]

I'm not sure why people go on with all sorts of speculation for things it's never going to be.

PATS CANNOT be enabled while driving.
EVER.

So there is no way at all that it has anything to do with this.
It should be 100% evident that it's due to installation error.



Now my guess is that this 'custom SRI' will resemble this:

Now how many times have we tried to help people and it's always been the black/orange wire has dislodged?
A hundred?
Ten thousand?
It's been a lot and the majority far as I remember.



Recheck your work and look for the wires you disturbed.

 

[sailor]

Yup, gotta have the one functional diode for the power to get to the PCM - doesn't give trouble often.

Second isn't used for that, part of the radiator fan control related to the A/C system IIRC so it isn't as critical. That's why I said a swap might be a quick check, like swapping relays for a test when there are duplicates used on different systems.

A lot of the forum hints are from remembering other similar situations, not all apply often so people try to suggest what is commonly seen over the odd situations.


Iminhell - X2 for sure, despite the sidetrack when the OP claimed not to have a chipped key. Another poster today was looking at the wrong wire even after a picture was posted.

 

[iminhell]

What happens when a diode goes bad?

The gate opens and current can flow in either direction.
They don't, normally in the Focus, fail and close the gate.

Again, not the problem.

 

[sailor]

Sorry for any confusion Bud, I was typing my last in response to something before your post & added a note to you while you were typing your last comment.

 

[Milton]

What happens when a diode goes bad?

The gate opens and current can flow in either direction.
They don't, normally in the Focus, fail and close the gate.

Again, not the problem.

A failed diode can result in an open circuit OR it could short out allowing current in either direction.

 

[Gooblanzee]

Oh sshiite, I completely skimmed over the part about the dash reading -------

Sorry for giving you false hope there.

If you can go without the car for awhile, you could disconnect the battery and let it sit for a good amount of time. This should reset the "keep alive memory" that receives a lot of data that is constantly changing, like the odometer and clock function and last learned running data like like MAF/coolant/throttle position sensor. I'm actually guessing about those specific items but I believe that's right. Leaving it unplugged for awhile cause the PCM to basically reset to a factory/known good condition, and upon startup it will use these "known good values" for things like ignition timing and fuel trim/flow. It's super easy and also worth a shot.

Really sorry about misses the info about the dashes, that's a big heads up entailing a totally unrelated problem.

Sailor, I haven't kept up with the forum and have never encountered this info about the diodea before the PCM/ECU. Makes perfect sense and it's potentially bad news.

OP, you should do some research and find some known good values for these diodes and be very methodical about your testing procedure. Any spike in voltage to the PCM can potentially cook the transistors in the PCM. Again, I didn't fully grasp until now the importance of those diodes. That's undoubtedly why there are two of them.

Honestly I'd love to say I follow, but as far as cars are concerned, I'm not nearly that mechanically inclined. Although I've always been good at rebuilding and fixing things, I've just never tackled something vehicle related as I'm only 18 and this is my first car. I don't understand all the terminology yet and I don't know everything that makes a car run. /: If you'd like to further explain in detail that would be awesome, I'd love to learn, but I also understand that may be surpassing what a newbie will be able to grasp. It sounds like you guys know how to go about fixing this though, so I'm all ears. I just need everything spelled out it seems.

Thank you all for the information, this is interesting to learn! []

 

[6SPD_soul]

Well, to begin with you really do need to double check that all the wiring you touched is fully intact and present. I would also be tempted to reinstall whatever intake was there before to see what happens, you've already got a non running car with what will most likely turn out to be a very simple thing. Might as well take 10 minutes and try that.

Since you kind of asked, here's how the mass air flow sensor actually works and influences the fuel/air mixture for combustion. The MAF sensor itself is simply a little wire with a precisely built and calculated resistance. On this car, and probably a lot of Fords for a long time, the PCM sends 5 volts across this wire in the path of incoming air. At rest and cold, the resistance in the wire eats up about 4 volts and the PCM sees a return voltage of 1 or thereabouts. Resistance in circuits naturally cause some amount of heat. When the airflow increases with driving conditions, more air is pushing past the wire and pulling heat from it. This alters the 5 volts going back to the PCM and it can match that return voltage with a corresponding fuel injector duty cycle to maintain a proper air fuel ratio.
It's such a simple device that it doesn't really naturally go bad, it may need to be cleaned occasionally because some exhaust gas is fed into the intake air for better fuel economy (whole different thing, don't worry bout it rocky : ) and some particulate matter can get pasted on the thing altering its resistance. Here is https://en.wikipedia.org/wiki/Mass_flow_sensor wiki link further explaining it.

I know that in my car, because the air filter box is right by the MAF harness connection and those wires are fairly delicate and kind of strained actually. A custom short ram intake is going to vibrate and move a fair amount and further the likelihood of an incomplete circuit right there at the harness.

That said I'm a little surprised my trick didn't work. Now that the dashes came up, I do remember seeing that those dashes a couple winters ago on a very cold day and I think after the car sat for awhile, and I kind of massaged the wiring at the plug and pushed them in to make sure they're fully seated, the car did start and then run normally.

 

[Gooblanzee]

Well, to begin with you really do need to double check that all the wiring you touched is fully intact and present. I would also be tempted to reinstall whatever intake was there before to see what happens, you've already got a non running car with what will most likely turn out to be a very simple thing. Might as well take 10 minutes and try that.

Since you kind of asked, here's how the mass air flow sensor actually works and influences the fuel/air mixture for combustion. The MAF sensor itself is simply a little wire with a precisely built and calculated resistance. On this car, and probably a lot of Fords for a long time, the PCM sends 5 volts across this wire in the path of incoming air. At rest and cold, the resistance in the wire eats up about 4 volts and the PCM sees a return voltage of 1 or thereabouts. Resistance in circuits naturally cause some amount of heat. When the airflow increases with driving conditions, more air is pushing past the wire and pulling heat from it. This alters the 5 volts going back to the PCM and it can match that return voltage with a corresponding fuel injector duty cycle to maintain a proper air fuel ratio.
It's such a simple device that it doesn't really naturally go bad, it may need to be cleaned occasionally because some exhaust gas is fed into the intake air for better fuel economy (whole different thing, don't worry bout it rocky : ) and some particulate matter can get pasted on the thing altering its resistance. Here is https://en.wikipedia.org/wiki/Mass_flow_sensor wiki link further explaining it.

I know that in my car, because the air filter box is right by the MAF harness connection and those wires are fairly delicate and kind of strained actually. A custom short ram intake is going to vibrate and move a fair amount and further the likelihood of an incomplete circuit right there at the harness.

That said I'm a little surprised my trick didn't work. Now that the dashes came up, I do remember seeing that those dashes a couple winters ago on a very cold day and I think after the car sat for awhile, and I kind of massaged the wiring at the plug and pushed them in to make sure they're fully seated, the car did start and then run normally.

Thats a pretty ingenious way of detecting airflow... props to the guys who came up with that back in the day lol. I'll try and look for a loose connection again as now I know what exactly I'm looking for. It could be that the wires came loose off of the connector itself because when the hood closes the filter makes contact with the hood itself. I thought this would be a problem but i watched how much it depresses the filter and it is only a few millimeters, so i thought that little of movement wouldn't be a problem.

(Next paragraph is more of a rant about the intake itself)

Now, as to reinstalling the factory intake system, that is impossible at this point. I decided that I would rather build my own intake from scratch than to buy too many fittings or a kit itself. So to build mine I took apart the factory intake and cut out the section or tubing with the air sensor inside. (about 1 foot of tubing) and made sure all connections were reconnected, then used a coupler to attach it to the throttle body and slapped the filter on the end. Now, apart from this being a jerry rigged way of making a SRI, I saw no problems with it as far as performance and maintaining the same hardware and had someone I am familiar with at the auto parts store help me design and install it.

(end rant)

And I would also assume that if the wiring was incorrect, the car wouldn't have started after the install, but it did and it ran much much better than stock.

Also, you say you can still run the car without the MAF sensor. I tried that with no luck, so the only thing in my small knowledge about this would be that something is wrong with the PCM as that is what is before the MAF in the circuit, right? Just trying to make sure I'm going about this correctly.

 

[6SPD_soul]

phuk, I keep missing essential info. I was thinking about a crank/no start scenario. You have a no crank/no start thing going right? That's the priority then.

Check this out on youtube https://www.youtube.com/watch?v=pJBMgrW7MQU it looks pretty damn relevant so far and deals directly with all your symptoms.

Seeing the electronic throttle body actuate when ground was re-established made it click for me.

 

[Milton]

Yes this is a NO CRANK-NO START-WITH DASHES FOR ODOMETER READING issue.
The "-----" is the first problem. It is most likely a problem with the PCM not being properly grounded or supplied with 12vdc or both. Since it worked initially after your mod we will have to assume you did not damage any wiring during the mod HOWEVER you state the the hood is hitting the filter which places mechanical stress on your SRI, all wiring attached to your SRI and everything your SRI touches. This is why you need to go over all the wiring you touched AND wiring you did not touch but which was affected by the stresses placed on the engine wiring harness and your SRI being depressed by the hood.
I know this seems stressful for your first seemingly simple mid, but hey you live and learn. "Modern" cars have smaller engine compartments with an increased density of components so a seemingly simple mod can have unforeseen consequences that show up a week or two later. Unfortunately we can not visually inspect the car for you. What we can tell you is:
-the "----" is the priority symptom, cure that and the no crank/no start may go away, don't cure it and the no crank/no start will never go away.
-the "-----" is most likely a PCM wiring issue (PCMs rarely go bad) so you need to check all the wiring. This may require removing your SRI to inspect wiring below your SRI. NOTE: You do not need to start the car to see if the "----" issue is fixed, just turn the key to the on/run position.
As for your statement about the PCM being before the MAF, I'm not sure what that means. The MAF is just one of many sensors that plug into the PCM providing the PCM with data on engine performance. Based upon these inputs the PCM adjusts things such as fuel injection, timing, idle speed, etc to make the engine run at "optimal" performance. When a sensor such as the MAF gets dirty and provides the PCM with bad data the PCM can make adjustments to the fuel/air ratio that cause poor performance, sometimes very poor performance. If the PCM gets no data from the MAF then the PCM uses a lookup table that says if you rpm us X then the amount of air going into the engine is approximately Y, so the PCM uses Y in place on the MAF input.

 

[6SPD_soul]

I really have to learn how to listen before talking LOL. And guys please feel free to call me out when I do that because it keeps happening, glossing over very important details and then writing entire books about side issues.

 

[amc49]

Look at the work done, odds are 80/20 the work has something to do with it............