Fuel Pump Relay not Grounding thru PCM

[robander3]

I've been having this issue for a long time and I haven't been able to find any resolutions.
Looking at the fuel pump circuit diagram (Page 50/0114-2 of the wiring diagram). It looks like the low-pressure relay isn't grounding out thru the PCM upon startup.
I have NOT checked to see if the wire between the relay and PCM is intact, but looking at the bundle of wires going to the PCM has no visible damage. I also can't figure out how to unplug the wires from the PCM, any advice here would be awesome too.
The low side resistor is at 0.4 ohms and works.
Jumping the relay allows the car to start and run.
Does anyone know the start sequence of the PCM, or what the PCM checks before grounding the relay (low pressure)

 

[robander3]

I've verified that the wire grounding wire between the circuit relay and PCM is good.
My Fuel Pump Resistor is at 0.4ohms. I have also bypassed that (for this trouble shooting).
I haven't been able to verify the PCM goes to ground for the circuit relay, but it does for other circuits so I have to believe the PCM has a good pathway to ground. I have no other issues that is controlled by the PCM. When the PCM fails is it usually multiple circuits or just one?

Also, if I ground the relay with the Check Connector the Fuel Pump does turn on.

 

[robander3]

Using ForScan I can see the PCM trying to turn on the Fuel Pump Relay when I turn the car on, while I'm cranking, and a few seconds after I stop cranking.
The resistance when the car is off I get a resistance of about 490k ohms. When I turn the car the on I get about 27k ohms, while cranking I get an open/infinity ohms. This is all measured from the Fuel Pump Relay to the ground/ (-) battery. I am on the forward relay pin for the PCM control.
Is this pointing to my PCM being corrupted/damaged and in need of a replacement?

 

[robander3]

I had to replace my PCM. Currently re-programming keys using forscan.

 

[RCP1990]

@robander3 did you happen to have any odb2 codes?

I think I might be experiencing the same issue.

- 9 out of 10 times, My car cranks but doesnt start.
- dont hear the fuel pump prime when I turn key to on but i do have power/ground at the 4 pin connectors.

was your replacement ecu new or used? did you marry it to the care yourself? can forscan do this?

 

[robander3]

@robander3 did you happen to have any odb2 codes?

I think I might be experiencing the same issue.

- 9 out of 10 times, My car cranks but doesnt start.
- dont hear the fuel pump prime when I turn key to on but i do have power/ground at the 4 pin connectors.

was your replacement ecu new or used? did you marry it to the care yourself? can forscan do this?

No codes, car right everything was working fine.

I did but a used one off eBay for less than 100. I was able to reprogram with FORScan. Do NOT delete keys already on the new PCM just add keys to it.

Do you hear the relay click on/off? Are you sure it's not the low speed resistor? Or bad relay, resistor?

My ECU fried because I think I put the fuel pump motor voltage into my PCM when I was trying to jump my relay to turn on my fuel pump. Classic case of knowing enough to be dangerous.

 

[RCP1990]

No codes, car right everything was working fine.

I did but a used one off eBay for less than 100. I was able to reprogram with FORScan. Do NOT delete keys already on the new PCM just add keys to it.

Do you hear the relay click on/off? Are you sure it's not the low speed resistor? Or bad relay, resistor?

My ECU fried because I think I put the fuel pump motor voltage into my PCM when I was trying to jump my relay to turn on my fuel pump. Classic case of knowing enough to be dangerous.

figured it out. it ended up being a bad circuit relay.