Hello at the Ranger-Forum,

Truck in question:
1999 Ford Ranger XLT, (early build)
4.0 OHV
Automatic transmission
4x4

Back story: My 1999 Ford Ranger is on its second engine. That happened in 2015. This past summer the old bed was removed and the frame repaired. Also, converting it to a flatbed. While the frame was off, I found why I was getting an EVAP code, a wire was broke at the vent solenoid to the vapor canister. Anyway, and sorry in advance to those who advocate not throwing parts at a vehicle, I decided to replace the fuel pump sending unit, pressure sensor and the vapor canister along with its' solenoid. Seemed like a fairly low cost way of avoiding future problems while I had the bed off. Anyway, while I was wiring a new pigtail for the vapor canister vent solenoid, I forgot to disconnect the battery. When I started the truck up and read the codes I got two pages worth of stuff. Holy-moly. After looking them over I soon realized I probably had a blown fuse. Replaced the fuse and Viola, most of the codes went away, except one, Code P0340. When I started the truck it ran rough. The fuse that was blown was the one that feeds the vapor canister solenoid, cam position sensor, all the oxygen sensors, and a few other items. Seven controls in total. All at fuse position 13. Amazed that so much stuff would be fed off one 15amp mini. One more thing, it is possible that the fuse blew due to me probing around the wiring harness to diag the cam position sensor. May have done something I shouldn't have.

The truck had been running a little rough before hand so I figured that maybe that code had already been there. I did not have a 'check engine' light. So, I was about to change the sensor and cam synchronizer but after doing a little research, I thought better of it. In reality, what really slowed me down was how nearly impossible it was going to be to get to the sensor and/or pull the synchronizer. It looked at minimum I'd have to remove stuff down to the fuel rail and perhaps even the intake manifold. A bit daunting for one stupid sensor. Come on Ford, geez?

So, did a little testing and here is where I'm at. Found the wiring diagram and PCM pin layout. This truck has a three pronged coupling (Hall effect). No idea whether this vehicle is pull down or pull up. DarkBlue/Orange wire goes to pin 85: cam position sensor. Black/white goes to ground. Light blue/Orange is shared with all three oxygen sensors and the tranny shift solenoids. Oh, and also with the fuel pump relay as will as the vapor canister vent solenoid. Actually, the fuel pump relay has a liteblu/org wire but I don't think it's on the same shared circuit as the others.
Battery voltage (been on charger all day): 12.17 volts (seems a little low for a battery being charged all day)
Readings back-probed at the CPS with key on, engine off:
Lt Blu/Org: 12.04 volts
Dk Blu/Org: 2.04 to 2.02 volts
Blk/Wht: 12.17 (red lead to pos. terminal at battery, negative to pigtail)
Pulled PCM coupling and probed pin hole 85 with long chubby sewing needle and tested continuity and ohms. Got good continuity back to the pigtail DrkBlu/Org wire at the CPS. Ohmed at 0.00.

So, the truck does not shift well and idles too fast, around 1000 to 1100 rpm. By now, no doubt most would have changed the synchronizer and CPS. Especially given how old they are. The sensor was replaced in 2015 but the synchronizer I'm thinking is the original. As I was thinking back, I do recall some squeaking going on that I could not locate. Now I'm thinking it was the synchronizer. A common problem with Rangers I'm finding out as they age and a sign of the synchronizer about to fail.

For sure this post is too long. My questions are the following: Since I'm not getting 5 volts on dk blu/org wire could it be that the ECM is bad as well or is that a normal Volt reading on that wire? I did try to get a wave form with a Pico Scope but got nothing but flat lines. I did, however, get a good sine wave from the crank shaft sensor. Also, I can not find a good 5 volt reference on any of the senors on this circuit (fuse position 13). The other question, will the intake manifold need to be removed to get to the synchronizer or just the fuel rail?

Thanks

 

1995 thru 1998 Ranger 3.0l and 4.0l did use a 3 wire hall effect Cam sensor, 12volt
In 1999 Ford change to a 2 wire Variable reluctance(VR) Cam sensor, these generate their own voltage, VR sensors are also used as crank sensors, speed sensors and ABS wheel sensors
VR sensors generate AC Voltage, 0.5vAC to 8vAC depending on the rpm of a tone ring, but the voltage is not "used", the sine wave frequency of the AC Voltage is "the signal"

But if you have a 3 wire plug and 3 wire sensor then it is hall effect, and should have 12volt wire, ground wire and the 12v on/off out signal wire
Black/white is ground wire
Light blue/orange wire is the 12volts, and yes its a shared 12v wire with O2 sensor HEATERS(not the sensor part) and the Transmission Solenoids, this 12v comes from fuse #13 in engine bay fuse box
Dark blue/orange is the signal out to pin 85 on the computer, this reads 12v then 0v as the cam spins the shaft in Cam synchronizer, there is a vane that interrupts the 12v as it spins, yes you would need "a scope" to slow this down to see it on a running engine, but you could rotate the engine by hand and see voltage come and go on this wire
No pull up or pull down circuit with this Cam sensor

Most other engine "sensors" do run on 5volts from the computer, reference voltage, and computer is also the reference ground, which is where pull up or pull down circuits come into play


Cam sensor in the 4.0l is just there to fine tune injector timing as it has more resolution that the crank sensor, spins at 1/2 the RPMs
Computer will set a code if Cam sensor(any type) is not in sync with crank sensor, and will ignore cam sensor until the problem is dealt with, on the 4.0l, with 3.0l cam sensor can cause other issues

If chasing a high idle and rough idle then warm up the engine and unplug the 2 wire connector on IAC Valve
RPMs should drop to 500-600, barely running, stalling would be OK as well
If not then vacuum leak 95% of the time

 

Thanks for the feed back RonD.

So then, since the dark blu/org signal wire should read 12v or 0v what might account for a 2.04 reading?

Also, I did not have a shifting problem with the AT until after the fuse blew. Could that point to a ECM failure on that circuit in the computer?

Thanks

 

Voltage on Signal wire would be meaningless if engine wasn't running, could be from computer end or sensor end, and if it was running then you would see 12volts I would image, depends on how fast the digital meter reacts to voltage changes, analog meter should pulse a bit

Fuse #13 powers the solenoids as well so shifting would be bad, and lots of P7xx codes and flashing OD light
Also the O2 heaters, so 3 O2 heater codes

P0340 is an electrical(circuit) issue which would also be a code that would come up if fuse 13 blew

Most common reason for fuse 13 to blow is an O2 sensor's 4 wire harness got too close to an exhaust pipe and melted, shorting out

So does fuse 13 still blow as soon as key is turned on?

 

I’m afraid I’ve made confusing the chain of events leading up to my problem. Fuse #13 has only blown two times. The first time was about three years ago when I was around 50 miles from home. Truck limped home. When it blew I thought the transmission was shot. It wasn’t until I got it home and got the fuse replaced that I realized that this is all that the problem was. Fast forward three years to this past summer. After removing the truck bed I found a broken wire to the canister vent solenoid. Now I’m thinking this was what caused the fuse to blow in the first place. When I wired in a new pig tail for the new sensor I forgot to disconnect the battery. Later when I started the truck I discovered the blown fuse. So it seemed logical to associate the blown fuse to wiring up a new evap solenoid given they are fed off of fuse 13. The fuse has not blown since replacing it this second time.

The poor shifting of the AT did not improve after replacing the fuse. It’s not horribly bad but has to get to a pretty high RPM before shifting. Not a smooth shift either.

I’ve not gotten any codes indicating a vacuum leak. Fuel trims are in a normal range. Only code is the P0340. The truck is in a shop getting a flat bed put on. When I get it back I’ll try unplugging the IAC as you suggest and see what happens. As I pointed out earlier, I did attempt a scope reading on the CPS but only got a flat line. Forgot to check what voltage the line was at. I’ll check again with the volt meter while running and a scope reading too. Going to replace the synchronizer and CPS after that. I have a new ECM programmed to my VIN but will not replace the old one until I’ve exhausted all other possibilities. I’m reluctant to change it given the problems with PATS keys. It looks as though I can use ForScan to reprogram them but I have my doubts.

 

Reaching out to RonD here. So, set out this past Friday to change the cam synchronizer and Camshaft position sensor but wanted to get getting a reading first and try pulling the connector on the IAC as you suggested. When I pulled the plug the idle immediately dropped to around 350 rpm from around 1200. It almost died but didn't. Shortly after this (and I'm not certain of the timing as I've lost track) but when I tried to start it the thing went a little wonky. Theft light flashed and it did a crank-no-start. I shut if off and disconnected the battery and did a parasitic drain test with my test light just to see if the PCM would do some kind of reset. After that the truck started like normal.

It was then I decided to change the PCM/ECM. Probably a bad idea. Put it in and did the ForScan PATS key erase/reprogram and module initialization. Everything went smoothly but then the truck only crank but not start. Pulled the intake hose off and sprayed starter fluid in the throttle body. It then cranked but still would not start without spraying starter fluid. Last night I put the old ECM back in and did the dance with ForScan again. Same result, crank-no-start. Then this morning took the intake hose off. I have to remove the TPS to get to the bolt on the hose so this time I left the TPS off. Viola, it started. And when I tried it again, it started without spraying fluid. So it starts without the Throttle Position Sensor attached to the throttle body. Can't make sense of that. It still plugged in to the wiring harness just not bolted down to the throttle body. What do you make of that?

A little more to the story. When I got it started the first time with the starter fluid I took it for a drive. It would not shift out of first gear. Today, after pulling the TPS off, it did seem to shift OK and it idled more like normal. Again, can't make sense of that. Your thoughts would be appreciated.

 

TPS does a few things, electrically, its a 5volt sensor, under 1 volt throttle closed, above 4.4v wide open
Its main purpose is to give the PCM a "heads up" when you press down on the gas pedal, MAF sensor is way too slow in responding to an air flow change, so engine would hesitate without the TPS
Secondary purposes are to allow PCM to shut off fuel injectors while coasting when RPMs are above 1,500 and foot is off the gas pedal, and it initiates "clear flooded engine" mode when at WOT
Clear flooded engine mode is in all PCMs
Key on engine off
Press gas pedal down to the floor and hold it down, PCM "sees" WOT(wide open throttle) at 0 RPMs, so it shuts off fuel injector pulses
Driver can then crank the engine over to dry out(clear) a flooded engine, spark is on, but injectors are off
As soon as TPS is no longer at WOT(foot off gas pedal) PCM will restart injectors even while still cranking
(I use this every morning when starting my high mile 4.0l, gets the oil circulated prior to allowing it to start)

IF(big if)..............TPS 5v and signal wires are shorted, then PCM would be in "clear flooded engine" with key on, so crank no start, but WOULD start by adding fuel manually

But that's just the electrical part of TPS
Mechanically it seals one end of the throttle plate rod, and it may also hold throttle plate open a bit causing a higher idle, or lets in more air so engine can start with throttle closed
IAC Valve should be open all the way with key on engine off, this provides the air for start up, and its why fuel injected engines usually REV on start up until PCM closes IAC Valve to set idle


Automatic transmission strategies are Fords territory, not a lot published on it, having a main sensor off-line, or cold trans fluid can cause delayed shifting for sure, so won't shift out of 1st until 3,000+ RPM unless fluid is warmed up
So I wouldn't think this was directly related to anything else

 

First of all, I'd like to thank you SO much for all your efforts to help people on this forum. It's above and beyond. I'd like to compensate you for your efforts in helping me. Just let me know how.

I am needing your input yet again.

So my question to you, Ron, is this: When I programmed the PATS keys with ForScan there is a module initialization that is needed. The only one I ran was for the PCM. I'm wondering if I should also have used initialization on other modules. Could you please share with me which modules interact with the PATS key system.
Thank you.

 

1999/2000 Rangers have a separate PATS module, its only connected to PCM via the data link wiring

The Key is read by the PATS module via the transceiver(just an antenna)
The number on the key is compared to the "programmed keys" in PATS memory
If a match is found then PATS module sends "OK to START" to the PCM
If no match is found then PATS module Flashes the THEFT light and PCM is disabled

The PATS Module and PCM are "married" at the factory, they share a private code(see RSA encryption)
Forscan should be able to "re-marry" a new PCM with the old PATS module, and program new PATS keys
Because the starter motor works and I assume no flashing THEFT light, you were successful in "marrying" the new PCM and programming the new PATS keys

If there is no flashing THEFT light with key on then PATS is not the issue so Forscan's response is correct, although P0340 is not the cause of a crank/no start
For some reason PATS module is not sending the "OK to Start" to the PCM

I have never used Forscan on a 1999/2000 Ranger so not sure on the module initialization to use, could be it is needed for the PCM to be "re-married"
Or could be PATS module issue, although I would expect failure in adding new keys if that was the case
And could be 1 or 2 of the data lines/wires are broken(between PATS and PCM), so PCM never gets the "OK to Start" from the PATS module, that would effect both PCMs

 

Thanks yet again, Ron.

I'm thinking (yes, this is a dangerous place) that perhaps I should have NOT used the module initialization function with the ForScan software on all the modules pertaining to PATS. I did the initialization on the PCM but not on the PATS module or on any other module that interacts with PATS. In addition, I was seeing several codes come up in regards to the GEM module. Does the GEM module interact with PATS as well?

Yet another question, I was attempting to remove the wire cover from where the wire harness plugs into the PCM. The thing just did not want to come off and I didn't want to force it too much as I was afraid I'd break something. Do you or anyone out there have any suggestions?

Thanks

 

No, PATS has no connection to GEM

There should just be a single bolt in the center of the PCM connector, unscrew it until it's not backing out any more
Then unplug the whole connector from the PCM
There are 4 tabs that hold the cover onto the connector, 2 are seen here: https://i.ebayimg.com/images/g/ZQoAA...z/s-l1200.webp
Then 2 on the other side

 

Thanks for the feedback, again, Ron. So, I was aware of the tabs that hold the wire cover on the PCM junction. Actually had them loose from the tabs at one point a few weeks ago, but, what I didn't notice (it was a little dark under the hood, my excuse) was the tape still wrapped around the incoming wire end. Duh, dumb me.

So, more questions for anyone willing to jump in. This past weekend I removed the camshaft synchronizer. Decided to go ahead and remove everything down to even the valve covers and lower intake manifold. The valve covers were leaking and there as a little oil leaking around the intake. What I discovered was that the camshaft synchronizer sits in position at a bit of an angle, jutting out from right to left looking toward the rear of the engine. So, maybe I could of wiggle it out without regiment the lower intake. Still, there were protrusions sticking out the back of the intake that seemed would make it a bit difficult. Anyway, covers and intake leaking so off they came.

 

So, in the above picture you can see the camshaft synchronizer at the back of the engine. I pulled it out this past weekend. Decided to bench test it. (Think that is the new one in the picture. Had to take it back out.) So, clamped it to a table. Connected from positive wire from battery to the blade that would receive the light blue/orange wire from the pigtail (12V), another wire from battery ground to ground blade (would be blade that receives black/white wire from pigtail). Then connected a third wire to middle blade to voltmeter and then turned the synchronizer with my hand. There was a clear on/off voltage reading of 12v when the vain on the synchronizer passed by the magnet on the sensor. Since I had the engine wiring harness nearly completely disconnected, I took it all the way out. I then determined where all the wires from the connector terminated and attached leads to these points. This would be just as if the sensor were sitting in the engine and hooked to the harness. Then attached 12v from battery positive to termination end of light blue/orange (power/12V), same with ground wire (battery negative to this termination on the harness). Then attached the Pico Scope to the harness where it would plug in to terminal 85 (dark blue/orange wire). Just eased a small finishing nail into where 85 would connect to PCM. Then spun the old synchronizer with old sensor attached. Got a clear 12V to 0V on/off wave form on the scope. Did the same with the new sensor. it too had a good on/off signal. (By the way, had to take the Duralast brand sync/sensor back cause the harness connector would not fit on the sensor end without using excessive force. Will try Standard Motor Parts nest. Duralast was made my Cardone).

Now I am confused. Each time I back probed the dark blue signal wire at the sensor to a voltmeter or the scope while in the truck all I got was a 2volt reading. This with engine running. A flat 2.0 line on the Pico Scope. What is going on? Does anyone see anything wrong with this test? What could account for the difference? At first, I thought, well maybe the gear that turns the synchronizer is broke so this morning I put the thing back in the engine and turned it over by hand. The synchronizer was turning. What do you think, Ron? Also, to clarify, I always got 12 volts on the light blue/orange wire at the sensor.

 

Not sure what the Hall Effect sensor signal wire(dark blue/orange) would show with engine running, volt meter of course wouldn't show pulses and should show a steady voltage but not sure what the voltage would be
Scope would need to be set to show a resolution slow enough to show the pulses, I don't use a scope so can't tell you what that would be

When you were testing the cam sensor off the vehicle and rotating it by hand was the signal mostly 0v and then became 12v briefly or mostly 12v then 0v briefly?
If it was mostly 0v that would explain the steady 2v

 

Thanks yet again, Ron! The voltage I got with the meter initially was right around 2.0V with the KOEO. At that time I did not fully understand how the thing worked. The sensor that is. I didn't realize that voltage signal was going to the PCM not from it. Yes, you are right. All you can see is average voltage on the DVM. When I did the PicoScope I back probed the dark blue/orange wire on the Hall effect sensor (middle blade/connection). I got the same voltage that showed on the DVM. Just a flat line on the cheap old laptop screen. This was true even with the engine running. The settings on the PicoScope software were such that I should have seen the wave form. Scale set at 0 to 20V and time laps I think was 20 ms.

I'm wondering if the sensor could be grounding out to the internals of the synchronizer. Seems unlikely given that it is in pretty much pristine condition. Was surprise how good it looked. Both the sensor and the synchronizer. Thought the next test will be to supply a ground some how to the shaft on the synchronizer and run the same test again. What say you? Also, there are still the wires that hook to the harness. Seems something is shorted to ground somewhere. Maybe the connector is bad but all the jostling around got it back to normal. It's a pretty short one wire lead from the sensor to the PCM.

 

Synchronizer is grounded to engine block, but its not part of the cam sensor electrical system
Synchro is just a vane the spins driven at cam RPMs
Sensor reads the spinning vane without contacting the vane

 

The VREF signal is very important. Backprobe at the ECU and ensure it is 5 volts. If it’s not, you have a short in the VREF circuit.

The ECU has a resistor built into it to ensure if there is a short, it does not fry the ECU. If this is the case, you will see the 2 volts you are seeing now.

Do this: unplug everything, one at a time from the VREF circuit. Monitor the VREF as you do. As you unplug things, if the VREF goes back to 5 volts, you’ve found the short.

Items in the VREF circuit include: TPS, EGR sensor, and fuel tank pressure. There may be others. This is what my 4.0 ohv has.

if none of those sensors when unplugged cause the vref to go back to 5 volts, now you’re chasing wires for a short, but I’ll bet it’s not a wire. My email is davelohrer@hotmail.com if you have any questions.

good luck,

dave

 

Thanks for Jumping in with some suggestions Dave.

 

Here is a bit of an update. After installing the new camshaft sensor and synchronizer AND finally having success reprogramming the new/refurbished PCM to accept my PATS keys the truck now is purring like a kitten. Now on to solving a few more issues. Namely, 4WD not going into low.

Was never really clear on what was wrong with the old 99. Had too many curve ***** going on. Extensive welding on the bed frame without disconnecting the PCM can't be a good idea I've got to think.

Gonna post some how to's on using ForScan to program PATS keys in another thread.

Yet another question for Ron. When I had the valve covers off, I noticed some plastic looking rings around the base of the push rods. Do you know what purpose these serve? Many of them were partially wore out.

 

No, never seen anything like that but never worked on a 1998 and up 4.0l OHV