99 Ranger turns over - no spark

[rustybolt]

Hey Fatboy! That's a good idea. However, I've tried the spare key which has almost never been used and the truck behaves the same way. If the regular key was damaged in some way that would cause the security system to lock out the ignition, you would think the spare key would allow the truck to start. But it doesn't seem to matter which key is used, the ignition system still would not fire up.

Today I spent some time checking sensor signals plus power and grounds at the PCM header connector. Everything checks out but the truck still would not run. So, I pulled the PCM out to have a look see and as luck would have it the unit has removable covers. Inside there were three easily identifiable FET's all clustered together so those had to be for the ignition coils. For yuks, I traced the path from the header pins back to the FET's. No problems found. I spent a good half hour going over the PC board with a lab type lighted magnifier looking for any possible sign of a cold solder joint. It all looks good. So then I reinstalled the PCM with the top cover off and then powered it up by turning on the ignition. There were several surface mount type voltage regulators that would be easy to check with the DVM so I poked around and found a lot of 5 volt regulators, all doing their thing. Sigh......

So, just for yuks, I jump into the drivers seat and give it another try. Engine started right up and ran perfectly.

I'm going to check with the Ford dealer and see if they have the means to test a stand alone PCM. Just to rule it out....

Back to Fatboy's point about the pats key, maybe the key isn't the problem but the device that reads the key???

Does anyone know how exactly the truck is suppose to behave if someone tries to start the engine with a bogus key? Does it just cut out the ignition system, like what I’m seeing? I would have guessed that the engine would not even turn over if someone tried to use a bad key.

Sorry for the windy write up....

 

[betomonroy]

That is exactly what it does.

 

[rustybolt]

Thanks for the post betomonroy... I've been told by a local garage that if a key with an invalid ID is used to start the engine (meaning the key is cut the same as the originals), the engine will start and run momentarily then shut down. Where as my truck wont run at all due to the ignition system not operating.

A good friend came up with an easy way to test for how the PATS system responds to an invalid key. Take the original key and wrap it in tin foil to shield the RFID module embedded within the key. This should prevent the PATS transponder from reading the key ID. Then try to start the engine and see how the system responds.

Since my truck engine is now running again (by magic), I'll give this a try and see how the system behaves.

 

[TomB1269]

I have a cut key that has not been programmed (my oh SHucks I locked my keys in key), I have tried it before and will again when I leave the office. But I beleive the other gent was incorrect, it will power up everything but it will NOT fire the motor.

 

[betomonroy]

I've seen it and done it nyself. You can have a cut key without the chip or a key with the chip that has not been programmed and try it. Everything will power up but the engine will not start. It will crank but will not start.

 

[rustybolt]

OK, that's positive confirmation then on exactly how the engine in my Ranger is behaving when it's in this mode. The other thing I need to look at when the engine fails to run is to see what the theft display in the dashboard is doing. According to the manual, that lighted word should go out after three seconds with the key in the run position which means the RFID was accepted. If it stays on solid or continues to flash after the three seconds then it's not happy with the key.

Thanks again for the helpful feedback. I'll post more this weekend. Hopefully the failure mode will assert itself again and I can try this PATS test...

 

[rustybolt]

Update, the truck has been starting fine all week. It's just sitting my garage collecting dust for now. Everyday I jump in and turn it over, runs fine. I'll just have to wait until it goes into that failure mode before continuing the trouble shooting process.. sigh....

 

[rustybolt]

Blast from the past update. It's been over a month now and the Ranger is starting normal every time. For anyone interested, here's what I can only conclude, that the PCM had an unreliable ground connection for the ignition. I traced the ignition circuit all the way through starting from the coil pack, to the PCM, through the PCM power FET's and then to the ground connection on the firewall right next to the PCM huge connector. The ground connection next to the PCM (on the firewall) was done poorly (in my opinion) but to the Ford's credit it's lasted 10 years and worked just fine. However, I completely disassembled that ground connection and cleaned everything, removing all corrosion and ensuring a good mechanical and electrical connection. Problem went away.

I also learned a bit more about the PATS security system used in this truck. Someone commented way back when that if the PATS system detects a key with the wrong code that it would disable the ignition and fuel systems but would allow the engine to turn over. I now know that's not quite true. If a key with the wrong ID is used to try and start the engine, the PATS system will completely disable the engine, including the starter. At least, that's how it works on my 99 Ranger. If you want to see it for yourself, just get some tin foil and wrap it completely around the ignition key and you'll see how your engine responds. The tin foil will prevent the energy emitted by the PATS transponder from reaching the RF ID circuit inside the key.

Now that my truck has been sitting in the garage for a month, I decided to take it for a short spin around the neighborhood. During the trip I noticed that the steering wheel would vibrate hard while turning the wheel through it limits. Never done that before. Maybe some air has worked it's way into the power steering fluid? Perhaps just driving around some will get rid of that. Any idea's???

 

[Bob Ayers]

I traced the ignition circuit all the way through starting from the coil pack, to the PCM, through the PCM power FET's and then to the ground connection on the firewall right next to the PCM huge connector. The ground connection next to the PCM (on the firewall) was done poorly (in my opinion) but to the Ford's credit it's lasted 10 years and worked just fine. However, I completely disassembled that ground connection and cleaned everything, removing all corrosion and ensuring a good mechanical and electrical connection. Problem went away.

The coil drivers are actually open collector bipolar (NPN) transistors. The emitters of these transistors are grounded through the ground you cleaned.

Thanks for the update!!

 

[rustybolt]

Hi Bob,

Thanks for the clarification on the devices used to switch the coil pack.

Best regards,

Chris...

 

[bigcountry]

i know on hondas that come into our shop if you use the wrong key the cars would not even turn on the radios wouldnt even come on the iginiton on the steering wheel would trun but that was about it but that is a honda not a ford but i hope the truck keeps running good for ya