Codes P0193 and P0183, fuel pump constant prime

Hi,

The PCM is what commands the FPDM. When the key is first turned on, it should actuate the pump for only one second until a signal from the crankshaft position sensor is recognized. If it is running constantly when the key is on and you replaced the PCM and FPDM, there has to be a short to power that is switched.

Okay, this is going to sound odd, but does the pump stop if the PCM power relay is removed?

I'm looking through the schematics and something has to be triggering the FPR. That signals (through the inertia switch) the FPDM. I'm wondering if the PCM power diode is bad and allowing power to back feed.

Inspect the diode. Don't jumper the circuit or install a fuse. Pull the diode and using a multimeter, check for continuity in both directions.

Let me know the results. Note: I attached a pic of the diode's location in the battery junction box. (Pic 1). The remaining pics are from the schematic.

Let me know what you find.

Joe

See pics below.

PCM power diode is showing open line no continuity on my meter.

Not sure if my voltmeter is capable of testing that diode from my understanding of the system is a fuel pump that has power all the time and the ground should disconnect to turn it off when priming in the ground as were adjust the fuel pressure meaning 50% 75% etc. My thoughts are now there’s a short in the fuel pump causing it to ground fully just been stumped.

My scanner is showing the fuel pump running at 70 PSI. Disconnected crank sensor, cam sensor, and every other sensor I could think of to find out where the ground is, to no avail.

Hi,

When you say open, do you mean there is no continuity in either direction? A diode should only allow power to flow in one direction. I need to confirm that is what is happening. If it is bad (and please understand this is a theory at this point), it could allow power backflow to the ground (G104 / front of right front fender) causing the issue. The power supply is via a switched power supply to the fuse. So, there is no power until the key is on and it doesn't stop until it's off.

As far as the ground, which specifically are you looking for?

Let me know.

Joe

I will replace diode tomorrow to verify.

Hi,

Please remember this is a theory at this point. I don't want you to spend money unless, we are sure. Is there any way we could check the diode?

Joe

Okay, I found another multimeter. I checked the diode it only has resistance in one direction, so it tested correctly.

Any more suggestions?

Hi,

Okay, at this point, I would likely remove one fuse at a time from the circuits related to the pump. Something is allowing power at all times. So, we need to limit possibilities. If you remove fuse 4 in the battery box, does the pump turn off?

Joe

Yes it does.

Also, if I remove that fuse with the ignition on the pump running the pump turns off if I put the fuse back in the pump does not come back on until I reset the ignition.

I guess the next step is replace pump then sent to shop.

Remove the fuel pump relay and check the dark green wire with a yellow tracer. That is the power supply that actuates the relay to send power to the pump. Is there power to it when the key is on?

Joe

I don't like it when someone figures out the problem and does not post it. Okay, the car has been repaired, I ended up replacing the fuel pump that was the problem. I bought a new pump unplug the old one plugged the new one in it ran three seconds to prime and turned off, so I moved forward and replaced it and it is working properly now.

Like I said this pump has power all the time. So, apparently there was a short to ground inside the pump motor. I don't like replacing things to find the problem, but I learned a lot on this. Hope this helps someone else.

Hi,

Thanks for the update. That's an interesting one. I'm trying to determine why it would get power if the prime cycle stopped. Regardless, I'm glad to know it's fixed.

Take care of yourself and please feel free to come back anytime in the future.

Joe

The way that system on a return less fuel pump is designed the fuel pump would have power all the time the ECM would give it a full ground for three seconds then it would determine fuel pressure with a pulse ground. Meaning 25% ground 50% ground etc. But apparently the fuel pump itself has a ground short causing full ground, which is why I had 70 PSI over pressurizing the system all the time.

That makes perfect sense. Thanks for the update.

I hope everything is still running properly.

Take care,

Joe