Codes P144A and P0193 (ugh..not again)

[AgentOrange]

Thank you!

Manual purchased!

Anytime, @honeybadger! I appreacite all the knowledge you and the others share on this forum as well. Once you have the manual you’ll find yourself looking at sections you never intended to be looking at....fun to learn random aspects about our cars.

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[Tomster]

Thank you!

Manual purchased!

If you need a copy of the section you are working on, let me know. My manual is for the R, but your issues should be the same as the standard 350

Edited to add, I just started investigating the P144A DTC and the manual treats it like a decision tree matrix. There are too many yes/no situations that take you in different directions. If you want, we can go one step at a time and I would be happy to feed you the next sequence of tests.

And for this reason, make sure you get the deluxe version. The deluxe version has all these steps hyperlinked so that you don't have to go searching around the 12,000 page manual.

 

[Tomster]

Step 1 DTC P144A

HX 10.... is the pressure within specification?

 

[honeybadger]

@Tomster - thanks! glad I opted for the Deluxe version.

So the purge valve opens (tested with 9v battery), the circuit that controls the purge valve is still good (passed my continuity test with a multi-meter), and I can blow air down the tube coming out of the purge valve. To me, this indicates that the first part of the EVAP system is good (the part in the engine bay). Obviously more in-depth diagnostics can (and likely will) be done, but I am hoping to check off the easy ones for the vapor canister/vent control in the back before I dive deeper.

When I followed the PCV line from the purge valve to the back of the car, I found it going under the rear diffuser into something directly under the spare tire well. I assume this is the vapor canister/vent control valve. It was the PCV tube coming from the front going in and 2 PCV tubes going to the fuel tank. My current hypothesis is this is where the problem is located - somewhere in the vapor canister, vent control valve or in those 2 other PCV tubes. I checked for physical obstructions, so I don't think it's that.

Do you see anything in the manual about testing the vapor canister/vent control valve?

 

[Tomster]

The manual is oriented more like a decision tree. It is very difficult to locate specific tests for various components. This is what I found for the canister and vent control valve.

I would suggest following the troubleshooting steps as per the manual for each DTC. Way too many variables and the decision tree takes care of the logic.

But here you go for testing the vapor canister vent control valve

 

[honeybadger]

The manual is oriented more like a decision tree. It is very difficult to locate specific tests for various components. This is what I found for the canister and vent control valve.

I would suggest following the troubleshooting steps as per the manual for each DTC. Way too many variables and the decision tree takes care of the logic.

But here you go for testing the vapor canister vent control valve

Thanks, Tom! I appreciate it. Looks like I know what I am doing tonight.

One of those times my signature is ever so true

 

[Tomster]

Thanks, Tom! I appreciate it. Looks like I know what I am doing tonight.

One of those times my signature is ever so true

If you ordered the manual today, you should have it tomorrow or the next day. Its worth every bit of the $130 or so I paid for it just for troubleshooting alone.

 

[Tank]

Jim, this is what the factory manual has yo say about carbon fiber wheels

I am out of town for Thanksgiving and do not have access to my computer that has the manual. They build the manual off of your VIN. However, it may contain instructions for both wheels. @tedj101 Will you please help @Tank with his question?

Thanks for your help @AgentOrange and @Tomster . The info was to try to wrap up the TPMS info in the GT350 Basics thread.

 

[honeybadger]

Welp, the plot thickens. So I tested the vapor vent control valve, PCV tubes going to the fuel tank, and EVAP canister circuit. All passed.

So I decided to power up the car, start it and re-read the codes. I had forgotten to plug the EVAP canister circuit back in, so it through a third code P0446. I plugged it back in, reset the codes and restarted the car. Surprise - no more codes. Engine seems to be happy as a clam. Ugh. It wasn't an exhaustive test session, but in 10-15 none of the codes came back.

Anyways, here are the details of the 3 codes.

Once I get the service manual, I'll test the circuits more in-depth. But right now, it's looking like maybe this is an intermittent problem. Considering both the purge valve and the fuel rails are controlled by the engine harness, I am wondering if there is a week connection that is going to cause me intermittent problems until complete failure.

If anyone else has ideas, I'm all ears.

 

[tedj101]

I am out of town for Thanksgiving and do not have access to my computer that has the manual. They build the manual off of your VIN. However, it may contain instructions for both wheels. @tedj101 Will you please help @Tank with his question?

Looks like Tomster already did...

<TED>

 

[honeybadger]

Alright, got the service manual out and started working my way down the decision tree. Since I have a GT350, I started DD8 per the instructions. Got to DD11 where I test the Fuel Rail Pressure circuit for a short to voltage.......where it failed. The f**k? How is it shorting to voltage? Exposed wires somewhere? oye

 

[honeybadger]

Not sure if I am suffering in the reading comprehension department or overthinking this, but digging deeper it says:

Fuel Rail Pressure Temperature (FRPT)
Sensor The temperature component of the FRPT sensor is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical voltage signals to the PCM corresponding to temperature. The pressure component of the FRPT sensor provides a signal to the PCM indicating fuel rail pressure.

The PCM supplies a 5 volt reference (VREF) signal, as well as supplying 5 volts on the FRP circuit. As pressure increases, the sensor signal voltage decreases. The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail and sends these signals to the PCM. The PCM uses the fuel pressure and temperature sensor inputs to command the correct fuel pump speed. The relationship between the fuel pressure and the fuel temperature is also used to determine the possible presence of fuel vapor in the fuel rail. The FRPT sensor is located at the top of the left fuel rail.

So the FRP circuit is supposed to supply 5v from the PCM, but the diagnostic parts say that if any voltage is present, there's a short to voltage (read step DD11 above). I must be confused...

 

[honeybadger]

Welp, I hooked up the PC, opened ForScan and pulled up the live voltage codes for the pressure sensor. I started to jiggle around the wires at the connector and watched as my voltage spiked from 2.2 to 5v and back. Looks like the wires busted.

I have no idea what those tech did, but they must've yanked on every connector imaginable. 3rd connector to fail on me. Ordered a new connector for now. When I can/need to do a clutch refresh or header install, I might just drop the engine and do a full harness swap. This is nuts.

 

[svttim]

Welp, I hooked up the PC, opened ForScan and pulled up the live voltage codes for the pressure sensor. I started to jiggle around the wires at the connector and watched as my voltage spiked from 2.2 to 5v and back. Looks like the wires busted.

I have no idea what those tech did, but they must've yanked on every connector imaginable. 3rd connector to fail on me. Ordered a new connector for now. When I can/need to do a clutch refresh or header install, I might just drop the engine and do a full harness swap. This is nuts.

And they strike yet again

 

[mustang_puppy]

Somewhat hijacking this thread but I had a CEL with P144A come up yesterday morning. I cleared it with a code reader but am weary of whether it'll pop up again and eventually mess up my car due to running rich. This purge valve that needs to be replaced is located under the cover just behind the backup light right?

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