Fuel system was ok other than fuel leak. Took into trans shop. Had trans replaced. Now gauge sits at E and low light is on, ck eng light is on. Check for codes, code po463 circuit high. Dropped tank, fixed fuel line leak. Pulled pump, tested varying resistance of float with multi meter. All appears ok, ohms vary when moving float up and down (pump is less than 1yr old) Pigtail connector appeared ok. Reinstalled, cleared codes. No fuel leak, code po463 came back on. Cleared again, on second start po463 high circuit came back. Traced for continuity from plug forward. trace ppl and org/blk. all good, found org/blk changes to gy/wht. traced to connector at trans. Cant access wires above trans to check further. Does anyone know where those wires go to? Where I should check for continuity next? I think they broke a wire, or didn't plug something back in when installing trans.I have alldata schematic for 2005, put pump plug is incorrect and so is color code. I suspect I made need a 2004 wiring schematic, the f/pump connector is flat like 2004, not square
I"M IN TROUBLE! NYS Inspect due, ck eng light on, will fail!

THANKS! I appreciate any input!

 

*moved to correct forum section*

 

What is the year of your truck?

George

 

I wouldn't get hung up on the connector design at the pump. The flat 4 pin connector is an upgrade that some pump manufacturers include with a new pump. The older square 4 pin connector could overheat on the main pump circuit and lead to an open circuit. The updated connector typically includes a length of wire on the vehicle side that requires splicing into the original harness. You may have to pull back the wire loom to inspect these splices. It is very possible that one or more of these splices is faulty.

P0463 indicates that the sending unit return is high meaning greater than 2.9V. The PCM supplies a 5V reference to the sender which is then modified by the sender in relation to the fuel level. The sender return is the purple wire at the PCM, connector C2 (red) cavity 54. I'm not sure if you can test this with C2 disconnected from the PCM, but I would try that first. The alternatives would be to pierce the wire insulation with a probe and then repair it after the fact with some liquid tape or attempt to back-probe this pin through the connector body which can be tricky without the proper equipment.

 

I traced the purple wire from the sending unit to Chassis harness connector at transmission. all ok. Cannot access other side of connector(engine harness side) Its too far up. Check continuity from Chassis connector to pin 54 on c2 at computer, it's open. Question is, I am considering just splicing a new wire from connector, lead it up to computer and splice it in to purple at cavity 54. Will I be bypassing anything important? Fuse/relay/ another circuit? Or is this a good Backyard fix that should not cause further issues?
I REALLY appreciate the input

 

Hi George,



I REALLY appreciate your input. Blazer is a 2005.Here's where I'm at; I checked continuity on purple wire from pump connector to harness connector chassis side at transmission. It's good. I can't get above trans to check further. can't even check the other side of attaching connector (engine harness) I check continuity from that point to pin 54 on c2, where purple wire enters computer. It's open, no continuity.
This problem happened AFTER I had the transmission replaced, and common sense says it's probably related, as far as a broken /pinched or disconnected purple wire. Of course the shop says not our fault.
My thought is to splice my own wire into the purple wire under the truck, lead it up to the computer and splice in there, by passing the open in original wire. What I am not sure about is if there is a fuse/relay or other component that I will be bypassing by taking the original purple wire out of service.

Could you please give me your input on this idea.





I am also trying to trace the second wire for the sender, blk/wht, low reference. I tried finding info on alldata, but cannot seem to find where that wire goes after the chassis connector. Would you have info on that?



I sincerely appreciate your help.


Have A Great Day!

 

I do not have the wiring diagram handy, but what I remember from it, the wire from the pcm to the tank connector is a straight shot with nothing else involved. Just make your splices 6" or more from the connectors to make sure you can reverse the change if necessary (i.e. Wrong wire etc...). Also, please double check the pcm pinout applicable to your year to make sure that there wasn't any changes from what I referenced (2000 model year).

The open circuit is troubling. If that were the case you should be getting a different code, one for low voltage or open circuit.

I'm camping right now so I can't get to many of my resources from my phone.

 

Power for the pump motor is a straight shot from the pump relay on the gray wire.

Ground for the pump is on the black wire from the pump to splice S423 and then to the ground G402 on the left rear frame rail

The purple wire from the fuel sending gauge is a straight shot to the PCM on pin 54

The other side of the sending unit is the black wire which first goes to splice S422 just a few inches from the tank. That then splits into two wires - a black/white goes to the fuel tank pressure sensor on top of the tank (let me know if you need the rest of that wiring). The other wire at the splice is also black/white but then changes to black then on to pin 23 on the PCM/low ref

Happy hunting.

George

 

Man do I appreciate the time your giving me. Thank you!


The pump works, so I know power and ground for it is ok. The purple wire, I replaced from the chassis harness before plug (good continuity from pump plug to splice) ran it up to pcm pin 54 after confirming 54 was correct. The truck is with the wife at work today, I'll let you know what I find. I'm using Alldatdiy to access some info. Their pinout for c1 and c2 shows pins 22 and 23 not used, but could be incorrect as I mentioned in one of my first posts.

I really understand the time and knowledge your giving me and am thankful for the help. I was in the Automotive Service Industry, A shop manager. I always explained to my guys the respect I had for them. I can say I did not have a true Diagnostic Technician for the last 15yrs. I sent those jobs elsewhere, I don't believe in throwing parts at a customers car, especially at their expense in dollars and time. Being able to trace electrical problems and track down codes is a real art. I could help them with my electrical common sense with these issues at times, but a Diagnostic Technician I am not.

Sincere Thank You

 

Ran a new low reference wire to pcm. Gauge working, low light off. Won't say its fixed till I put miles on it, but all looks good, ran it a couple times, no pending codes. I'll confirm it in a couple days THANK YOU