Hello everyone,
I finally signed up for this forum since I have been using it for over half a decade. I signed up because my 1998 Mazda B4000 with the 4.0 OHV has a P0340 code that makes me want to tear my hair out.Let me start from the beginning. I had the camshaft synchronizer and the camshaft position sensor and the wiring to it replaced not too long ago because I had a P1309 code. About six mouths later I got a P0340 code. I took my truck to the mechanic who did the original repair. They said the camshaft sensor was still in time with the engine. They did recommend I change my plugs and wires since the truck did have a slight misfire. Since this was an easy task, I did this myself. Afterwards, the truck did run and shift better, plus it had more power. On the other hand, this did not get rid of the code. I did search not only this forum, but other Ranger/ explorer forums. I even looked at a Mustang forum. Other users did say the alternator may have a bad or failing diode and this may cause this light due to the dirty voltage. I took off my alternator and took it to a local auto parts store to get it tested. It the machine said it passed. Looking at the printout, It has 0.49 volts of ripple. Is this too high?? I do not want to waste my money on unneeded parts. Right now, the truck runs pretty well. It does have a valvey sound when the engine is under heavy load. Any help is appreciated. I hope what is said here can help others with their problems.

 

AC Ripple under .50 ACvolts is passing, so .49 is passing but................

It needs to be tested at higher RPM so can't say how auto parts store tested it, at what RPM

To test it in the vehicle it is pretty easy
You need a Volt meter with AC volt setting
Locate B+ connection on the back of the alternator, the Stud with the larger wire connected
Start engine
Have someone raise RPMs to 3,000 and hold it there
Test AC volts by touching 1 meter probe to B+ and the other probe to Alternator's Case(ground), there is no +/- with AC Volts so color of meter probe doesn't matter

You want to see under .50 AC Volts

1998 Cam Sensor shouldn't be effected by AC Volts in any case, 1998 and older used Hall Effect Cam sensor, 3 wire sensor, 5voltDC and ground sensor
1999 and newer Ranger V6 engines used 2 wire VR(variable reluctance) sensors which outputs AC Volts, so could/would be effected by alternator leaking AC Volts

But the AC Volts can effect other systems so good to test it in any case.

Is your Cam sensor 2 wire or 3 wire?


OBD Codes are many, lol, and the code the computer chooses to use is important
But also important are the codes the computer DID NOT USE
There are many Cam sensor codes, computer picked P0340
Code list here: OBD-II Trouble Codes

Computer did NOT use
P0341 Camshaft Position Sensor Circuit Range/Performance
P0342 Camshaft Position Sensor Circuit Low Input
P0343 Camshaft Position Sensor Circuit High Input
P0344 Camshaft Position Sensor Circuit Intermittent
These all mean the circuit is working but not well


It did use P0340 Camshaft Position Sensor Circuit Malfunction
So to me this would be either a wiring issue or computer issue
The circuit is the problem, not the sensor
Now it could be the sensor is broken inside so there is no circuit
But if sensor is replaced then could be a wire is broken
Or circuit inside computer is broken

A Circuit is a loop of electrons flowing
For DC electrons flow from + to - and if you remove either the + or the - then electrons stop flowing, if computer detects no electrons flowing it sets P0340, circuit is open, somewhere.

If electrons were flowing too fast or too slow, or were flowing off and on then computer would set the other codes for this

And electrons actually flow from - to + but that's another story, lol, and not important to this problem
For AC electrons flow back and forth, they "alternate" direction, hence the name alternating current, or AC, but to flow they still need a circuit, minimum 2 connected wires

 

RonD, thank you for replying. I really appreciate it. I took out my multimeter and put one side on the B+ on the alternator and the other on the case. I used the MAX button on my meter. At 3,000RPM I have 0.338 volts AC. Strange how it is lower than the parts store test. I also looked at the connector to the camshaft position sensor and it is a 3 wire connector. I forgot to put this in the original post, I reset this code four or five times. It never comes on while driving. It always comes back when I start the truck. This Light does turn off sometimes when I am on the highway giving it some gas, but it always returns later. I does take awhile though.The shop would notice if there was a wiring problem while they were probing the sensor with a scope, correct? A PCM issue is pretty hard to troubleshoot without getting a used one and swapping them right? I understand it is hard to troubleshoot anything over a computer screen, but do you have any more suggestions? Again. Thank your for helping me.

 

Yes, hard to say how some places test electrics, always best to test it yourself in most cases

If you have a Volt meter then I would test the Cam sensor wires
First test battery voltage with key OFF and then key ON
Key On voltage is what you need to remember, i.e. 12.4volts, or 12.6volts
A "good battery" will test as 12.3v to 12.8v
New battery is 12.8-13.0v
5/6 year old battery 12.3v
12.2v or lower is old or bad battery, time to replace it

Cam sensor wires, remove connector from sensor
Red wire should have 12volts with key on, battery voltage as remembered in above test
Black/white stripe is a Ground
So check that Red wire has 12volts, but by grounding meter to engine or battery Negative

Then test using the Black/white wire as the ground
Move wires around while testing, watch for voltage drop

The Dark Blue/orange strip wire is the signal that goes back to computer, it runs directly to Pin85 on the PCM(computer) connector
Need to use a sewing pin to peirce that wire at the PCM end and do OHM test, meter probes at each end of that wire, 0 ohms is good connection

If possible, disconnect the Coil Packs 4 wire connector, so you will have a No Start
Have someone Crank the engine while you watch voltage on the red wire, it should drop down to about 10volts, if it goes under 10volts then Computer could "read" that as a bad circuit.
As a car battery gets older it can't store as many AMPs and can't release them as fast.
So there is a larger voltage drop when starter motor is active, it still starts the engine, but system voltage drops lower.
Colder weather also effects speed with which battery can release AMPs
Also older starter motors tend to draw more AMPs so the combo of older battery and older starter motor could get to much of a voltage drop

This is a long shot, but your comment of "when I start the truck" made me think of it

No, shop wouldn't check wiring specifically, they would look for frayed wires at connector of Cam Sensor

 

Okay, so I used my voltmeter to test the battery "key on" voltage. It was 12 volts. Let me mention I replaced the battery in January. At the alternator, the key on voltage is 12.5 volts. When I got the new battery, I got new terminals and wire brushed all the wires going to the battery. So do not think it is a connection problem there. On the other hand, I did take a peek under my truck and noticed my starter was covered in oil and grit. This is due to a oil leak I had in the past. My question is this causing a voltage drop to the battery? I will try and clean my battery terminals/ wires/ and connectors one more time just to make sure it's not them.

The cam sensor wire did have 12 volts exactly on it when the key was in the on position. I flexed the wire around, but this did not change anything.

I ohmed out the ground connection and it was a dead short to the motor which is good. I jacked the cable around and it did not change.

I also did the ohm test to the PCM and it was also a dead short to the end of the connector. This also did not change when flexing the connector and cable.

I disconnected the coil pack and hooked my volt meter up to the side of the connecter that reads 12v and had my wife crank the engine over. She said it did not drop below 10 volts.

Again thank you for helping to continue to troubleshoot this.

 

Outside of engine temp issue(165deg) I think you have done all you can and it is down to PCM issue

 

What do you mean by engine temp issue?

 

Sorry wrong Code, was thinking about another thread with catalyst monitor test, where engine temp is an issue
You have tested wires and sensor so all that is left is PCM error

 

Thank you though for your help. Is there anything special i need to do to change the PCM besides finding one with that is from the same year, engine, tranny. Does it need to be flashed?

 

Before going out and changing your PCM, clean you ground strap running from the fire wall to the back of the engine _ clean all grounds while you're at it.
Ford painted them green for some reason, so the paint prevents a good ground.

I had a PCM error as well, and it went away after I cleaned the grounds.

Also, my 99 had this white lithium grease all over the connections, including the engine wiring harness and the PCM.
I had to clean all that crap out of there with lacquer thinner and compressed air.
I replaced with a clear dielectric grease to keep out moisture and dirt.

It was a tedious job going through all the sensor connections too.

The last harness I did is when my gas gauge stopped working, the harness plugs underneath the cab had that same grease that had to be cleaned out.

 

I apologize for the delay, but I finally got around to cleaning all of the grounds on the truck and no luck. I also returned to the mechanic who originally replaced the synchronizer, sensor, and connector and asked them to replace all three again under warranty . Astonishingly, the same code still appears after awhile. Would a intermittent signal from the crank position sensor cause a fault code like this? Is that something I should investigate? Also, would a faulty coil pack cause this fault? Again I am sorry for the late response and I really appreciate your help.

 

Hi,

So my sensor and synchronizer (99 4.0L OHV). I was getting the P0340 randomly. But every once and a while...infrequently, I would get a code for the coil pack. I had bought new pack and just carried it around. So I also replaced that when doing the sensor/synchronizer. What is interesting is the original synchronizer and sensor seem to be fine. At the time of the change out, the only code I was getting was P0340.

Note sure if that helps

 

Hi, i fiound a p340 and p300 codes, but no engine fail or other symptoms. A year ago i changed CMP connector but it was working until a month ago. Could you help me?

 

Please go here and start your own thread.

Also be sure to include year and engine
https://www.ranger-forums.com/newthr...newthread&f=33