Hello everyone,

I have been having an issue with my 2005 4.0 v6 4x4 Ranger XLT. I was driving going about 80 on the freeway and it just stalled, no check engine light and no codes were stored on the computer when I scanned it with a snap on scanning tool at the shop. It did it several more times on a smooth flat country road at about 35mph on a warm spring day. Each time when it stalls I can start it immediately after turning the ignition off. Dude at the shop said it was a problem with the IAC valve and/or the MAF.

SO I went ahead and cleaned the throttle body and replaced the IAC, the MAF, the fuel pump in the tank as well as the filter and the ignition switch (got all the stuff for a super good deal and figured what the heck). The idle runs a little lower now (700 compared to 1k previously) than it ever did before but seemed ok. I took it up to see my mom (about a 300 mile drive) and I had no problems at all. I took it off road for 30 miles on a terrible stretch and had no problems (other than blowing a cv boot). A day later I was driving down my driveway (graded dirt road decent downhill slope) and was riding the brakes a bit and it stalled again but started back up right away.

Since then it stalled once more at a stop light but started right away as always. I live in a pretty busy area and don't wanna risk crashing it into someone so I stopped driving it. Now that I cant go into work I figured I would reach out for help on this and hopefully get it solved. I cannot for the life of me think of whats going on and its super unpredictable about doing it.

Any help would be much appreciated!!

 

Welcome to the forum

From the description I would say your computer(PCM) is shutting down
When key is on and engine is OFF you should see the CEL(check engine light) on
The CEL is controlled by the PCM directly
If PCM is off then no CEL
So if your engine was stalling from lack of fuel or bad sensor then CEL would come on at the time the engine was at 0RPMs with key on, same as it does before starting engine

Do you remember if CEL came back on after engine stalled but before you touched the key?

If PCM is shutting down then there would be no Codes because there are no codes generated when you turn off the key, cut power to PCM, its normal operation

There is a PCM Relay in the engine fuse box, it powers up the PCM, it is possible for it to be bad/failing, though its a long shot
It could be ignition switch under the steering column, may be loose enough to be cutting power to PCM relay shutting down PCM, and turning key off and on reposition's ignition switch so PCM relay comes on again and all is well

And its possible for PCM itself to shut itself off, although a longer shot than even PCM relay

The ONLY sensor that can stall a running engine, above idle, is the Crank Position sensor, its the spark and fuel timing sensor, its the only sensor that can cause a no start as well
But if PCM was on at the time...........it would for sure set a code for CKP sensor, because Cam sensor would still be sending an RPM signal at that time

 

SO I was driving it to the store yesterday. Made it a mile and then it died and I had a no crank no start for about 5 minutes. All the dash panel lights come on when the key is on as well as the stereo and lights I cycled the key about 5 times. I also plugged in my little ODB2 reader and I got a yellow light with no codes (its an Innova 2030b). After the 5 mins i Got it to crank and not start and then it started and instantly died twice. I gave it a few more seconds and it started up and drove with no CEL. The PCM relay is pretty warm to hot t the touch when I left it running in the driveway (so are the fuel pump and fog lamp relays that are directly behind it) the ones in fromt of the PCM relay are not nearly as warm.

So far I have replaced the MAF, IAC, TPS, and the ignition switch as well as the fuel pump in the tank. Previously this happened and then I was able to drive 300+ miles with no issues. I had it scanned with a high end SnapOn scan tool at two different shops and no major codes other that the TPS out of range so I replaced it.

It was about 90 degrees yesterday when I decided to go to the store (although this has happened in a wide range of temps but most commonly why warm/hot out). I was thinking I should replace the PCM relay but I am concerned about driving it around as this thing dies randomly from 50mph to stopped at a light or parked in the driveway so I am trying to avoid an accident.

Can Ford diagnose the PCM with their scan tools if its an intermittent failure? My scan tool is indicating that some of the modules are either not finished with their scan or not responding while in accessory mode. I can start it and it runs though. So its super random and real frustrating only 117,000 on it and its super clean so I was hoping to get a little more use out of it before major problems.

Thanks for the response! Let me know what you think.

 

2005 Ranger does not have PATS(passive anti-theft), Ford skipped this one year in Rangers

2005 Ranger has an HEC instrument cluster, digital cluster

Google: Ford HEC test mode

Read about running thru the tests and see if the cluster has any Codes that may point to something

Was the CEL on when key was on, and no crank?
When it started to crank again did the CEL go OFF when cranking?

The CEL means PCM is on
The CEL going off when cranking means the PCM "knows" you are trying to start engine, its getting a crank sensor pulse

There is only 1 sensor that can stall a running engine, the crank sensor, and that WOULD set a code, 100% of the time
There is no sensor that can cause a No Crank, well clutch switch or DTR can
PCM can't cause a No Crank, in 2005
No crank is purely an electrical issue

The starter motor activation power path is like this:

Ignition switch in START(12v)-------(Fuse 21 in cab)-------(clutch switch or Trans switch)--------(starter relay, engine fuse box)---------starter motor

Manual trans uses a clutch switch(on the clutch pedal), clutch pedal must be down all the way to pass the 12v on to starter relay
Automatics have a DTR(digital transmission range) switch(on the transmission), only passes 12v when in Park or Neutral

The starter relay in engine fuse box SHOULD BE GROUNDED by the PCM with key on, in a 2005 Ranger, in other years this would only be grounded when using valid PATS key
If PCM is not grounding this relay then No Crank, but for sure wouldn't cause a stall

I don't think Ford has any way to test a PCM, there might be a software update available for your VIN, you can call and ask, 15 years old is at the edge of service so they may not have anything available to them, but worth a call

You can test PCM by unhooking, say the MAF sensor, then starting engine, should get a CEL pretty quickly, for No MAF
Then clear code and plug it back in, then unplug TPS, start engine, should get CEL pretty quick again
ECT........

You can do that with a few sensors to see if PCM is doing what its suppose to, like a "sanity check"

You can pull out Starter Relay in fuse box, and with key on test for a slot with a ground, pin 44 on PCM is suppose to be a ground for starter relay
You can manually ground this relay, to take PCM out of the loop

Yes, by all means replace PCM relay or swap it with another relay with similar layout, maybe wiper relay, or AC relay
PCM and fuel pump relays do run warmer when engine is running, 10-20amps run thru them, most other relays are half that when activated

 

Hey Ron,

Thanks for the info. I have done the sanity check with the MAF and it will throw a code for that. As far as the CEL going off while cranking I was not checking that and seeing as the problem is so intermittent I don't have a way to test it again until is decides to act up again.

I did pull the relay this morning to check and see if it might have some visible damage to the relay itself of the box that holds it but didn't find anything noticeable. I did however find another issue that got more extreme after pulling the relays this morning. When I start it it will bog down real bad and then surge back up immediately after starting so I am not sure what could be causing that now as well. There is still no CEL.

I know that this cannot be a purely fuel/air issue as there is the problem with the no crank no start as well. Do you know of anywhere I can fuss with to try and replicate the issue to try and pinpoint what is doing this?

At $225/hr the local ford dealer is going to take me to the cleaners messing with this thing and provided I dont need super expensive diagnostic equipment I am pretty well set up to do most of the stuff on this thing myself.

Hoping to give it to my niece who is about to graduate, just not the way it is now.

Thanks again!

 

I would try this, pull out the PCM relay and see if you get a No Crank, it has no connection to starter activation EXCEPT for grounding the starter relay

If its a no crank then yes, this could all come down to the PCM, and I know of no way to test it specifically, and I doubt Ford can either

The PCM Grounds the fuel pump relay and starter relay, and PCM has several external grounds it uses internally, and they are NOT "shared" grounds, if one of these ground circuits was failing then that could cut off fuel pump, or spark(also needs ground) and then also do a No Crank right after
As far as I know Ford never released circuit diagrams for the PCMs

You could check with local wrecking yards, but you do need a 2005 only Ranger or Mazda 4.0l with matching trans(manual or auto), 2WD or 4x4 doesn't matter for PCM

You can get rebuilt for under $150 I think

 

So I just pulled that relay and got a no crank when I tried to start it. You think this could be an issue with the relay having problems causing it not to start until the relay decides to work again? or just a PCM issue all together?

 

Well that depends on if the CEL was on with key on and you had a No Crank

If PCM relay works the CEL comes on because PCM booted up, and if there was a No Crank(because starter relay wasn't grounded, still guess there) then it would be an internal PCM issue

If there was a No CEL and No Crank then yes that would point to PCM relay not closing with key on

And I assume it did crank and start with PCM relay plugged back in?

 

yes, it starts with the relay plugged back in.

No CEL with the relay pulled.

I am going to take this thing for a drive and see if I cant get it to do it again. If it dies I will look and see if the CEL light is on.

I want to say that when this happened before and it died with the key on the CEL light came on when i tried to crank it over and got a no crank no start. At the cost of going to the shop it might just be worth buying a new PCM and shoving it in there at this point.

I don't really see what else it could be, especially given the fact that the no crank and no start followed by the crank no start would be different systems having trouble and their common thread is the PCM.

Thanks for all the info. I will post back here if I can get it to die again.

 

Yes, if engine stalls with key on, CEL will come back on at around 0 RPMs, no crank sensor pulse

CEL will go off when engine starts to turn from starter motor working, that means Crank sensor is working and PCM see the timing pulse

Obviously a No Crank wouldn't turn CEL off, and shouldn't

Yes, it does seem to come back to PCM, and the irregularity of it also points at PCM

A wiring issue would be more repeating I would think, a bad external ground for the PCM maybe but I think that would be more repeating as well