So I'm throwing code p0452 which is evap emissions pressure sensor, aka fuel tank pressure sensor, aka boost sensor. Reading low.

I replaced the sensor, nothing. I replaced the gas cap, nothing.

What are some common causes? Any help is appreciated! Yes I cleared the code. I'm using the torque app on my android with a Bluetooth obd2 reader. Awesome tool.

 

So after some further diagnosing, i am getting voltage to the purge valve, and to the sensor. i noticed that my purge valve seemed to be stuck open, so i replaced it and cleared the codes. A few miles later, the code is back! ggrrrrr

for the record, i replaced the fuel tank pressure sensor with a used unit from the junk yard. these things are like $150. i might have to do a pressure test here soon before investing in a new sensor.

for those who dont know what i mean, to test the sensor, you unplug it from the canister, hook it up to a pressure source(manual pump) and read the voltage signal to see any fluctuation. there is a video on youtube on how its done.

if anyone has some advise, please post up. otherwise ill be researching how to diagnose a bad evap canister. i don't see any holes in my evap system, next step would be the canister itself...or a brand new fuel tank sensor. sigh.

 

Check the rubber ring on your fuel pump.

 

update: purge valve did not do the trick.

Thanks DD. i will check the fuel pump ring. Any other advise?

 

Checked fuel pump gasket, good shape. What else could it be?

 

OK so i figured out what the issue is, but not sure what the cause is.

The canister purge solenoid is not shutting. I bench tested the solenoid with 12v, and it closed just fine. So i tested the plug, and i AM getting 12v. Here is the weird thing, as soon as i plug in the solenoid, the voltage drops to 0v so the solenoid is not closing.

I did a continuity test for the ground wire all the way to the ECU, and there are no breaks. Does this mean my ECU is bad?

has anybody encountered this problem?

 

After further trouble shooting, i came to realize that there is a break in my ground wire for my fuel tank pressure sensor. There should be continuity at the plug ground and chassis ground, but there is not.

i believe this is why the vent valve is not opening because it is not seeing an accurante sensor reading.

i tore my whole car apart last night looking for a break, and i couldnt find it

anyone know where i can find a wiring diagram for a 2003 g35 sedan? More specifically i want to know where the wires run that go from the fuel tank pressure sensor ground wire--->ecu

thanks guys

 

Anyone? I really don't want to pay a mechanic...

 

Can someone tell me which pin comes from the ecu to the fuel tank pressure sensor ground?

I'm thinking that maybe my ecu is busted, but if I do not have continuity from the pin to the plug, then I know it's a wiring issue...

Thanks.

 

I think you've already proven you're more knowledgeable than anyone left on this site. Most of these kids are probably still wondering what "continuity" means. I doubt you'll find your answer here. Try my350z.

 

I've been a mechanic for over 30+ yrs and have done my fair share of wire tracing and all. But this car has me stumped.
I've replaced both sensors with brand new not used at the evap canister, checked all hoses, wires, voltages. Replaced both the fuel pump assembly and sending unit with new gaskets (seated correctly). The only one that i replaced used is the purge under the hood at the corner of the plenum. BUT it does work because if I unplug it it will throw a code. Ive checked everything I can think of and still the P0452 code keeps coming back. Oh and i changed the gas cap as well with a new one...

Sorry to bring up and old post, only thing i could find close to my issue

Any help from someone who has the knowledge or been through this would be greatly appreciated 🙏.

 

That code isn't for the EVAP solenoid in the engine bay or the valve on the canister, it's for the PRESSURE SWITCH mounted on the side of the canister. It's separate from the canister and plugs into it so you probably still have the original faulty one installed.

There are two EVAP solenoids, one mounted on the canister, one mounted in the engine bay, and the pressure sensor mounted on the canister.

That code means it's an electrical issue, not something else faulty with the pressure sensor. You can unplug the pressure sensor and use a DMM to check voltage and ground to see if it's just a wiring problem.

Black/yellow stripe - 5vdc
Pink - 2 to 5vdc scaling
Black/white stripe - continuity to ground

Here's what it looks like, and a picture of the EVAP canister with it installed.

 

Hey brother I appreciate the reply but as stated I've already replaced the EVAP control system pressure sensor with a brand new one. Have also check the wires and plug. All is good.

 

Ok then check for those voltages next. Here's the wiring diagram, each of those 3 wires on the sensor goes straight back to the ECM. If the harness looks like it's covered in grime (likely) and/or if it looks like gas has leaked out onto it then use a PLASTIC SAFE electrical contact cleaner to really clean out the harness and the sensor. Just give it a few minutes to dry out before plugging it back together.

If it's still throwing a code take the same power and ground readings from the back of the ECM harness, just backprobe those pins carefully, then see if it's all the same readings.

I'm guessing you're going to find a melted/damaged wire somewhere though. You might end up just running 3 new GPT wires back to that sensor, splice into the harnesses, then abandon the factory wiring. I think it all runs up through the cabin and penetrates down through the back seat with the fuel pump wiring.

Harness F102 / M72 is the big super multiple connection right next to the ECM under the glove box. It's where the engine main harness breaks out to the chassis harness. You should inspect this one for any water damage, if the battery box isn't draining properly (pretty common to have the drains clog up but you will usually also have IPDM problems) then water can seep into the cabin and damage that harness.

Harness B1 / M12 is the super multiple junction next to the BCM in the driver footwell. Same thing, inspect it for damage/corrosion. If the vehicle has a sunroof the drains at the front cowl can get clogged up (common issue) and the water like to drip right down on top of that SMJ.

Make sure to disconnect the battery before unplugging any of those harnesses.

 

Ok nice! I'll check it soon as I can and get back asap.