2008 X-runner fuel pump circuit issue

Long story short- Truck will not run. When I ground the wire for the C/opn relay, the truck runs. Pin 10,plug E8 on the ecm. FC circuit. I believe this is the wire that times the pump on/off if you have key on/engine off. i.e on for a couple seconds, then off. If the engine fires, it keeps the pump on. No DTCs. Are there any special conditions for this circuit?

 

Toyota does not run the fuel pump at key on, it only turns on when the PCM sees a Start signal and/or an RPM signal from the Crankshaft Position Sensor.

Your saying the PCM isn't turning the C/OPN relay on even while cranking?

 

Does your tach move when cranking?

 

He said it runs with the relay grounded (PCM control bypassed) so I assume it has crank sensor signal.

 

DM93- correct. Fuel pump does not turn on during crank.

Discovered a new related issue- FPR signal is not releasing the fuel pump relay for the fuel pump to go into high speed for hard accel. If I disconnect that wire from the ECM, I get full pump power. This problem I noticed a while back. I don't drive the truck much, and frankly would've never found the problem. Had no idea the fuel pump operates in 2 speeds.

 

Small edit- checked codes and I have 02 heater codes p0031 and p0051 which shouldn't effect this.

 

Are you sure the wire is good from the PCM to the C/OPN Relay?
I'm not exactly sure what the parameters are for the PCM to switch the pump to high speed but I do know they start in high speed and switch to low speed after the truck starts.

Here's the OEM diagrams and pinouts.

 

FC (blue/blk) is good because thats where I'm grounding it. I depinned it from the ECM plug and grounded it to start the truck. The FPR wire is good because I depinned it from the ECM to release the fuel pump relay and get pump high speed.

I'm learning signal NE is from the crank position sensor. NE tells the ECM 1. to turn on c/opn, and 2. change the fuel pump relay between high and low speeds. Funny though, I'm not getting any crank codes (per HP tuners scanner).

 

Since it runs when you ground the wire and you have no crank sensor codes I would have to assume the crank sensor is fine.
If it refuses to ground the C/OPN relay and it's getting an STA signal and a crank signal it seems the PCM may have failed.
Have you checked all powers and grounds going to the PCM?

 

Yeah I'm thinking the same once the ECM. I wondered too about grounds and power but if I did, I would have a lot more codes. 104k miles fyi. I used to be a Lexus tech and Toyota ecms have always been pretty rock solid.

FYI, I have a same generation pre runner- automatic. Not a fan of swapping electronics around, but, maybe?

This prerunner was a freshwater flood and I replaced the ECM and immobilizer about 10 years ago. Refresh my memory. Can't you leave the key, immobilizer, and ecm powered on together for an hour and they'll accept each other?

 

You have to do the registration, it takes 30 min but that's all you need to do to make the immobilizer happy.

If the PCM is the same year model it should run the truck but it will set a bunch of transmission codes if it is an automatic PCM.

 

Ok, got a used ecu and got it to register. Half of the problem is gone. It starts and runs so c/open is operating correctly.

The issue is the Fuel Pump relay. The FPR signal is holding the relay in low speed mode. If I pull the ground side wire for the FPR out of the ecu connector, my fuel pump defaults to high speed mode and the truck operates normal (sort of, still runs a little funny).

The tac appears to operate normally so in theory the crank sensor is operating normally. On HPtuners the throttle body and TPS seem to follow correctly. Unfortunately I can't view the crank signal with my HPT.

Any ideas?

 

What is the truck doing that leads you to believe the the PCM is not switching the pump to high speed when it should?

Is it stock?

 

When I disable the relay that switches modes, the truck runs fine (defaults to high speed). Return it to normal, it is staying in low speed. You can ease the throttle, but once you mash it, it completely chokes out.

 

Another note: there's a solenoid that applies vacuum to change the intake runner length. At a stop in neutral, it's not changing as you rev it.

 

It's likely not going to switch the fuel pump or runner control just sitting there reving it, it has engine load tables to determine when to switch.

It sounds like you have another issue, have you checked your fuel pressure?

 

When I remove the ground to the relay, it drives fine. Pressure is good.