Interesting Failure

Keith from Collinsville Diagnostician Posted   Latest  
Discussion
Driveability
2001 Chrysler Sebring LXi 2.7L (U) 4-spd (41TE)—1C3EL56U31N506973
P0352 - Ignition Coil "B" Primary Control Circuit/Open

So this vehicle has been fixed, and will not be too difficult to figure out, but I figured this would be fun. 

This 2001 Sebring 2.7 came in running horrible, It would run "OK" for a minute, then the closer to op temp it got the worse it would run. 

Fuel trim was actually fine at +/- 4% LT & ST

Blue trace is cylinder 5 coil primary on the switched side

Red trace is the ASD fuse current measured with a clamp at the PDC

Here is a screen shot!

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Brandon from Reading

   

Diagnostician
   

Keith, I’m on the road… But it looks like you have a driver hangin’ up. My next step would be to include CMP/CKP because they are inputs responsible for ignition timing and dwell. 

Of course there is the possibility of an actual short-to-Ground on the driver circuit ...

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Keith from Collinsville

 

Diagnostician
 

You would be correct brother! I fixed this one last week. I looked at CKP/CMP it was good, but I assumed so as injector pulse was normal. PCM fixed it.

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Albin from Leavenworth

 

Diagnostician
 

It looks like you have the problem cornered. My next step would be to go directly to the PCM, monitor the voltage and current at your cylinder 5 pin. Your trace looks like either there is a short to ground in the coil negative wire, or the driver in the PCM is hanging closed.

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Keith from Collinsville

 

Diagnostician
 

I did current at the PCM for cylinder 5 and had current from the PCM indicating the PCM was holding ground itself. I fixed this car last week, a PCM was the issue, I just dont think ive ever had one that the PCM was holding the driver on and I caught it on a scope.

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Geoff from Lahaina

 

Diagnostician
 

Thank you for clarifying the issue KP. I usually think I know what I am looking for, and then a scope-shot confirms it. I find looking at other people's traces and then trying to reverse think-it is "not really my thing". I focus on the wrong stuff. Like, what is wrong with your coil #2?

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Keith from Collinsville

 

Diagnostician
 

I was really hoping someone would ask about number 2, the only code in the PCM was for cylinder 2 coil primary circuit fault P0352. 

I am assuming here, but due to cylinders 2 and 5 being companion cylinders, i am guessing that the two coil drivers share some connection, a common internal ground, or digital to analog voltage converter or something.

After PCM replacement the pattern was rechecked and confirmed to be good. So im not 100% what the correlation is.

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Tom from Santaquin

 

Owner/Technician
 

I am working on one and the pattern looks similar but it's a a/c circuit turn on a/c or defrost and eng. Dies 

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Sean from Forest Lake

 

Technician
 

The amperage stays elevated in the area I circled, but the voltage seems to return to an open circuit (or close to it)? Or is that slight drop in voltage on channel A during that time the PCM driver still partially grounding the circuit? Just trying to make sure I understand what I'm seeing. Thanks!

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Keith from Collinsville

   

Diagnostician
   

It measures around 1 volt lower than battery voltage, so i am assuming you are correct, as that was my thought as well. The PCM does not appear to fully release the ground.

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Geoff from Lahaina

 

Diagnostician
 

looks like, even with the one driver partially latched, the ECM is trying to keep running everything else.

Quite the opposite of all the Chrysler that just die when ANYthing is out of whack and set no codes.

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