2005 Chevy Silverado - 5.3 Vin T - Fuel Guage Not Working - 333k miles...

I have a 2005 chevy pu in my shop that is starting to make me mad.... There were several problems with the truck when it came to the shop on a Trailer. Most important was the fact that it would run about 100 yards and then it acted like the transmission would stop pulling... the truck would stop and not move in any gear... the Truck has over 333k on it... I dropped the tranny pan and put in a filter and cleaned up things some... I figure that the filter will stop back up before long and the transmission will need to be rebuilt.
The next thing was the oil pressure gauge and the fuel gauge was not working... I suspected the gauge console since these trucks are known for gauge cluster failures.... but to be on the safe side I through an oil pressure sender on it and the oil pressure gauge worked... on to the fuel level gauge ... I raised the bed and took an ohm reading on the sending unit wires... the circuit was open... so I put a fuel pump on it. I had decided that it was possible for the fuel level gauge system to have two problems so when the fuel level indicator did not work I was not too surprised... I sent the cluster out for a rebuild.. got it back today and popped it in... still no fuel level indication.- The gauge reads empty and the low fuel light is on.... I have access to Mitchel on Demand and have the complete drawing and am very good with electrical issues.
I was going to back probe the fuel level sensing wire but when I uncovered the PCM I find there is no way to get to the back of the connector to back probe anything on the PCM - Also the fuel gauge along with all the other gauges show on the print that they are "Ignition Class 2 Data". All the other gauges are working - all the powers and grounds are good to the cluster ...
There is a circuit that leaves the cluster on pin B7 a yellow wire that is shown to be "DIC Fuel Sig" the circuit goes through the inflatable restraint steering wheel module coil and then a switch in the Steering Wheel then back through the restraint module - then to the IP Relay Block and then to Ground...
So I have a couple of questions... Does this DIC Fuel Signal circuit have anything to do with the Fuel Level Gauge?? What does DIC stand for.. Does the fuel level gauge operate from Class 2 Data sent from the Computer??? How can I tell which plug on the PCM is C1 and C2... Is there a way to get the cover off of the C1 and C2 PCM plugs or do I have to puncture the wires once I figure out which plug is which...
Thanks in Advance if anybody knows the answers...

only if you had a bidirectional scanner to do a gauge sweep test. what does the fuel level read in the ecm?

DIC = Driver Information Center

CTRL + F in this pdf for more info about the Driver Information Center

my.chevrolet.com/content/dam/gmownercent...silverado_owners.pdf

Does the fuel level gauge operate from Class 2 Data sent from the Computer?

From reading the wiring diagram, yes it appears so.

There is a circuit that leaves the cluster on pin B7 a yellow wire that is shown to be "DIC Fuel Sig" the circuit goes through the inflatable restraint steering wheel module coil and then a switch in the Steering Wheel then back through the restraint module - then to the IP Relay Block and then to Ground.

I believe that is a computer pull-down switch input button that's on the steering wheel (that's why it goes through the inflatable restraint steering wheel module coil) to show "Fuel Range" information on the digital display.

From the pdf:
"Fuel Range: Press the fuel information button until
RANGE appears on the display. This mode shows the
remaining distance you can drive without refueling.
It is based on fuel economy and the fuel remaining in
the tank. The display will show LOW if the fuel level
is low."

I believe if the fuel range says LOW on the digital display, then it there's probably nothing wrong with the analog gauge. Maybe wiring issue or pump level sending unit issue.

(I am reading from the Engine Performance Circuit, Except Hybrid diagram)

As for which plug is C1 and C2, you could count the wires going to each and match them up with the wiring diagram. I believe on Mitchell's wiring diagram, C1 is on page 1/5 and C2 is on page 5/5 (Engine Performance Circuit).

If page 1 of 5 of Mitchell's Engine Performance Circuit shows C1 and page 5 of 5 shows C2

Connector 1 pins 1-5 colors are:
BLK/WHT
LT GRN
PNK/BLK
LT GRN/BLK
EMPTY

Connector 2 pins 1-5 colors are:
BLK/WHT
BRN
TAN
EMPTY
TAN/BLK

C1 has 20 empty pins, 80 pins total, so C1 has 60 wires

C2 has 23 empty pins, 80 pins total, so C2 has 57 wires

Yeah, I don't think that DIC Fuel Sig thing has anything to do with the actual fuel level indication. You'll probably see the little Fuel button on the steering wheel. Looks like a gas pump, if it hasn't worn off at 333K miles. :lol:

I'd do as Cheryl suggested, as far as bidirectional controls and scan data first. That'll tell you if the PCM is getting signal from the level sender without more pinpoint testing.

If that's not an option, you can also track down the right PCM pins and do some resistance testing. C2 pin 54 purple/white and C1 pin 23 black are the fuel level sensor wires. Most GM level senders work between 250 and 50 ohms, so you're looking for something in that range. Anything else is irrational and will likely set a code.

Speaking of, any codes in the PCM?