Quick advice for a French owner struggling with P0340 code

sab said:
Hey, Maverick26_Fr, I've learned something new in another thread that may explain the 5V on the signal you're seeing with the crank sensor unplugged. Apparently there are pull-up resistors inside the PCM that keep the signals at 5V nominally. See the posts after the initial one in this thread:

[URL]https://wranglertjforum.com/threads/crankshaft-camshaft-position-sensor-voltage.72437/[/URL]

Knowing that, I no longer believe your PCM is the issue.
Click to expand...

Hello Sab ☺️

Thank you very much for your message (appreciated) and these information. I was a quite worried by the PCM replacement

So I will try to cut and weld some wires on both sensors signal in order to investigate more.

If someone has an advice about an oscilloscope model which I can buy on amazon.. 🙂 . I will ask too some friends to see if they have that in a garage..

I have had an Hameg in the past (electronical school matter), but I sold it 10 years ago.. not thinking that it could be useful again!
 
dbbd1 said:
Here you go...

https://www.amazon.com/gp/aw/d/B091Y41PJ6/ref=ya_aw_od_pi?ie=UTF8&psc=1

I still have an old Tektronix o-scope.
Click to expand...

That’s the one I have. It was kindof hard to calibrate, but eventually I got it. I’m pretty happy for the $30 investment, BUT it won’t tell you *everything* you need to know. It will tell you if your cam or crank sensors are putting out a reliable square wave. 98% of the time that is the problem. WHY it’s not sending the square wave will remain a mystery to unravel.

It won’t tell you if those two are properly in phase with each other. They make a dual channel arduino based scope that is like $100. It’s tempting. But unless you suspect that your timing chain jumped a tooth it’s probably not going to help you diagnose anything.
 
I went back to the initial post to remind myself what were actually chasing down here. @Maverick26_Fr have you bench tested the cam sensor? It’s very easy to do. My video shows it for a non-distributor style but the process is exactly the same for a distributor-style sensor. Removal is easy too. Remove the cap (don’t even have to unplug it, pull the rotor (aka the finger) straight up & off. Then lift the black thing that looks like a cover of sorts; it’s the cam sensor. Unplug it and bench test it.

Also, might as well post a pic of what it looks like under there. Let’s take nothing for granted.
 
hear said:
I went back to the initial post to remind myself what were actually chasing down here. @Maverick26_Fr have you bench tested the cam sensor? It’s very easy to do. My video shows it for a non-distributor style but the process is exactly the same for a distributor-style sensor. Removal is easy too. Remove the cap (don’t even have to unplug it, pull the rotor (aka the finger) straight up & off. Then lift the black thing that looks like a cover of sorts; it’s the cam sensor. Unplug it and bench test it.

Also, might as well post a pic of what it looks like under there. Let’s take nothing for granted.
Click to expand...

Hello after holidays without Jeep 😞

I still haven’t bought a scope but with a simple voltmeter I can see that the voltage on the Camshaft sensor signal pin is variable when I cranck, so I guess that it’s working well. I have replaced the original part by a new one and this is the same issue. So I’m not sure that it is necessary to buy a scope no? Maybe this could just confirm that the square wave is good and not damaged.

Also, in order to be sure that there is no interference in the harness, I have tried too to cut the wire on the PCM connector, (pin 18 Camshaft sensor signal), and weld it directly on the sensor connector: same issue.. 😔

But a little thing makes me suspecting the PCM:

I have previously noticed a 5v on the crankshaft signal pin female connector (when sensor is disconnected) => we have concluded that it was normal due to an internal resistor in the PCM. So Ok for this 5Volts

But when I check the same thing on the camshaft sensor signal pin on the female connector (still with sensor unplugged) I have only 1,6 volt.. maybe not normal .. I guess that I should obtain the same value for this sensor. Any opinion? Is it easy to open the pcm and check visually electronical components?

And it’s a pity but from yesterday I have a new error code added to the previous one P0340. I guess that I have might created it after making all these tests on the sensors and harness:



IMG_6497.jpeg



I have found a little Jeep skilled garage at about 1 hour and I am currently wondering if I can give them the car to let them continue to investigate.. 😤

Thank you for your help!
 
  • Like
Reactions: Wranglerfix
I feel terrible this is your experience with a Jeep, especially that far away. I'm going to read through this thread again in the morning with fresh eyes. Honestly though, if it were me here, I would have swapped out the PCM because easy and then the harness because I still think that's what it is. Are you okay with throwing a few parts at it?
 
SkylinesSuck said:
I feel terrible this is your experience with a Jeep, especially that far away. I'm going to read through this thread again in the morning with fresh eyes. Honestly though, if it were me here, I would have swapped out the PCM because easy and then the harness because I still think that's what it is. Are you okay with throwing a few parts at it?
Click to expand...

Thanks for the message, I appreciate your help ☺️

Are you able to advise for a US company which should sell me in France a PCM configured as well (I have disabled the rockwell 10years ago)?
 
  • Like
Reactions: Wranglerfix
Maverick26_Fr said:
Thanks for the message, I appreciate your help ☺️

Are you able to advise for a US company which should sell me in France a PCM configured as well (I have disabled the rockwell 10years ago)?
Click to expand...

If it's just a matter of shipping it to you, I don't mind turning something around and sending it to France for you if you had it sent my way. Some companies just don't want to deal with shipping outside the country regardless of the cost. I had an American car overseas as well so I can sympathize with your struggle to get parts.

And something didn't translate correctly with the rockwell bit. Is that the security key immobilizer thing? For earlier models like ours, as long as the immobilizer isn't an issue, the PCMs can be swapped from car to car as long as the transmission is the same.
 
Last edited:
Hello @all :)

This message to update all members who have kindly tried to advise !

As a reminder : no ignition with P0340 code displayed on a basic ODBII Wifi reader with Car Scanner app
- Crankshaft sensor replaced + check 5V OK
- Camshaft sensor replaced + check 5V OK + new wire direct from sensor to PCM
- Ignition coil voltage OK
- Check OK +5V on all sensors (magnifold, t°..)
Note that the original anti-starting box (rockwell) has been disabled (disconnected 10 years ago when Jeep was running).

After a long search, I have found a local Jeep skilled garage who has towed my jeep.

They have swapped my 97 TJ PCM manual transmission by a 98 TJ PCM auto transmission (they had no TJ 97 PCM available locally) :

-> Ignition is now OK 🙌 BUT no fuel injection 🤬 : the PCM doesn't put the 6x injectors to the ground so there is no injection, as soon as we crank the Jeep. The specialist told me that if it was an anti-starting issue on this PCM (Rockwell), the jeep would have run 5 seconds before the injectors were deactivated.

Note that the fuel Pump is OK, and the ASD is OK.
They have tried to read defaults with their ODB reader : no error codes.

Do you see some test to run to identify why the PCM doesn't activate injectors?
Do you think that a TJ98 PCM automatic transmission instead a TJ97 PCM manual transmission can causes this issue?

Thank you a lot by advance 🙏

Kind regards



1696343131831.png


1696343153908.png
 
97-98 PCMs are interchangable as long as SKIM isn't an issue. The auto PCM will eventually throw a code if it doesn't see the TCM.

You said you verified the ASD circuit is not being tripped?
 
SkylinesSuck said:
97-98 PCMs are interchangable as long as SKIM isn't an issue. The auto PCM will eventually throw a code if it doesn't see the TCM.
Click to expand...

You sure about that? The only place the computer interacts with the 32RH is the torque converter lockup solenoid, which will eventually throw a code, so I think you’re ultimately right but for the wrong reason.

I lose the sorts of debates with my wife all the time so I have to collect a W whenever I can. 😝
 
  • Haha
Reactions: SkylinesSuck
Yes, you are probably right. It doesn't see something from a slush box it doesn't like and throws a code, but still runs just fine, I know that.
 
  • Like
Reactions: hear
SkylinesSuck said:
Yes, you are probably right. It doesn't see something from a slush box it doesn't like and throws a code, but still runs just fine, I know that.
Click to expand...

For sure, you just lose the TCC, which may not even be a thing depending on your usage.
 
Top Bottom
Back