P0353 - Need Assistance...

[Ocnaj]

Hey all, I recently purchased a '97 SHO that needs a little bit of work. I couldn't pass the deal up for the car since it was only $450. The main problem it has is a miss. This is the first 3rd Gen SHO I have ever owned.

I pulled the codes and the only one that pertains to the miss is P0353(right?). Other codes were: P0500, P1131, and P1414.

So I pulled everthing apart. I made sure that the rear coil harness wasn't melted or any of the wires weren't broken and they were fine. Then I replaced Coil 'C' with a known good coil and I still have the code and the miss. Is there something else I'm missing?

Correct me if I'm wrong but Coil 'C' is also Coil '3'?

1 - 2 - 3 - 4 _ A - B - C - D

5 - 6 - 7 - 8 _ E - F - G - H

 

[SHOZ123]

Yes C=3.

Is it a steady all the time miss or just an occasional one?

 

[Ocnaj]

It's a steady miss. Thanks for the quick reply Paul.

 

[SHOZ123]

Then you need to see if there is 12V at the coil when it is running. All the coils should have a constant 12V when running and share a common circuit so if this would be the problem then it would be on the short piece of wire. The PCM switches the coil ground individually so this wire would go back to the PCM. You need to see it is is good all the way with an ohm meter.

I would not trust any used coil, know good or not. Look for minute cracks on the body below the connector.

I have a bunch of new coils if needed.

 

[Ocnaj]

So white w/ blue stripe is constant 12v?

And the other wire that is specific to the coil is the signal ground?

How much are your coils?

 

[SHOZ123]

Yes, the white/pink wire is the switched ground from the PCM for cyl # 3.

 

[Ocnaj]

Yes, the white/pink wire is the switched ground from the PCM for cyl # 3.

This wire is pin 27 on the PCM correct?

Where do the coils get the constant 12V from?

 

[SHOZ123]

"Where do the coils get the constant 12V from? "

White/Light Blue wire comes from the interior fuse box.

White/Pink wire is term 27 on the PCM.

 

[Ocnaj]

Well, I replaced the coil with a brand new one (Thanks Paul). It cleared the code, however, it still has the miss. I'm not really sure where to look now...

Could it be an injector? Wouldn't an injector also throw a code?

 

[SHOZ123]

If it is a steady miss it may be the +12V going to the coil or the PCM switched ground, or the PCM. I would look closely at the wiring going to he coil for melted insulation.

 

[Ocnaj]

If it is a steady miss it may be the +12V going to the coil or the PCM switched ground, or the PCM. I would look closely at the wiring going to he coil for melted insulation.

I checked the +12V with a multimeter and it was good. I also checked continuity of the switched ground from the coil to the PCM and that was also fine. I also checked the whole rear coil harness for any breaks, melting, etc. Didn't find anything. Is there any way to check the PCM?

 

[SHOZ123]

You can backprobe the PCM connector for the coil ground trigger wire and see if it is switching on and off when running.

 

[Ocnaj]

How would do that?

 

[SHOZ123]

With an ohm meter.

 

[Ocnaj]

With an ohm meter.

I meant, how do you backprobe?

 

[SHOZ123]

I use a short piece of solid wire around 20ga or so. Like found on a florescent light ballast.

 

[Ocnaj]

Do you put the wire on the back of the PCM connector?

 

[SHOZ123]

Yes you just slide it in there.

 

[Ocnaj]

Ohhh ok. So you take the terminal of the coil ground that you want to test and insert the backprobe wire that you want to use. Start it up and see what you get correct? What would be a normal reading?

 

[SHOZ123]

Well with ohms it will be switching so fast you will have a hard time getting an actual number. If you set he meter on AC and stick the other probe on the battery + post you should see an ac voltage number.

Either way you want to see some rapidly changing values, 350 times a minute or so at idle.