2018 Chevy Silverado k3500 fuel signal wiring
Customer dropped off this Silverado 3500 can and chassis with a complaint of low power intermittently. I scanned the pcm, and the current codes are P228B, P228C, and P2635. Identifix shows that all 3 codes are almost always a fuel sender issue. On the datastream, the secondary fuel level shows 1.06 volts, with intermittent spikes to 4.98 volts while. The is actually an access panel in the flatbed right over the sending unit, and I scoped it, but I only read .22 volts on the signal wire, and a square wave 5 volts on the low reference. Data shows 4.98 volts with it unplugged. According to the wiring diagrams, both wires are supposed to go to the fuel pump driver, but the repair info states that cab and chassis is different, but doesn't state what the difference is, or where it is. I tried locating it, and I cannot. What I am trying to do, is scope the signal at the driver, but I need to know if this application even uses one, and if it does, where it is. I would also like a better description of how this circuit is supposed to work with a square wave reference. I have never seen that before.
What do you mean by wrinkled? Top of tank is covered in stucco, and I had to chisel it away to get to the sending unit. Bed is loose, and I will look at that once I get it on the hoist to change the oil.
There is a service bulletin about dirt stopping up tank vent and collapsing tank hard enought to bend the sending unit .
Not collapsing at all. I am more concerned about the square wave on the reference, which I have never heard of.
Is this pump different than most ..most diesels they just run all the time engine is running..have you checked fuel pressure .pump not running at all would or could cause the main common rail pump to not profuse max pressure ..especially if is pulling thru a dead tank pump ..I have not worked on a l5p yet but it’s just a denso instead of bosch
Any time you get 4.98 Volts on a signal wire that means you either lost the sensor ground or the signal shorted to the 5V ref. It is most likely a pin fit issue with the sensor ground for the fuel sending unit at least.
I understand that, what I don't understand, is why the scope reads .22 volts, even when the data is acting up, and why there's a square wave reference when al I have ever seen is voltage, or ground that pulls the signal wire down, or up. I am reading .22 volts regardless of whether it's plugged in, or not, back probing, or straight to pin with it unplugged. The pid reads 1.06 unless I am…
It has been a month,and the issue appears to be gone. The flat bed had come loose, and the 2x4 that was between the bed, and frame was pushing on the top of the rear tank. I lifted the bed, put the 2x4 back, and bolted it back down. I talked to him yesterday, and he stated that once it showed reduced engine power on the dash with no loss of power, but his actual low power issue seems to be…