What does it mean?
Rather than a permanent open or short, this code records a tank temperature signal that behaves unnaturally over time. A thermistor in a large gas tank has a lot of thermal mass behind it, so its reading should drift slowly by a few degrees at most over several minutes. When the module sees the value jump many degrees between samples, disappear briefly, or bounce between extremes, it flags the circuit as intermittent or erratic. Almost every cause is a mechanical connection problem in an exposed underbody environment, made worse by road salt, water spray and vibration. Since the module briefly accepts each bad sample before rejecting it, the driver mainly notices a gas gauge that behaves oddly rather than a running problem.
Symptoms
- MIL (check engine lamp) that appears and clears without any repair
- Gas gauge that jumps or momentarily drops to empty
- Range display that fluctuates unrealistically
- Occasional refusal to change over to gas that resolves on the next start
- Fault most likely to appear on rough roads, in heavy rain or after washing the vehicle
- Nothing reproducible with the vehicle standing still in the workshop
Likely causes
- Loose, corroded or fretted terminals in the tank sensor connector
- Water inside the connector that bridges pins intermittently and then evaporates
- Chafed harness that touches ground only when the vehicle flexes over bumps
- Cracked internal joint in the thermistor that opens with vibration or temperature change
- Intermittent open at a corroded body ground point
- Harness routed too tightly, so it tugs on the connector as the tank moves on its straps
- Loose connector at the gaseous fuel control module
How to fix it
- Read the freeze frame to see the conditions when the code set and plan the test drive around them
- Graph the tank temperature value on a scan tool while an assistant wiggles the sensor connector and harness under the vehicle
- Open the connector and check terminal tension, contact face condition and the seal, since water intrusion is the leading cause here
- Follow the harness along its entire underbody route, looking for chafe points at the tank straps, heat shield edges and body brackets
- Voltage drop test the ground circuit while tapping the loom to expose an intermittent open
- Repair or replace the affected terminals, reseal the connector and secure the harness so it cannot rub, then verify the trace stays smooth on a road test
- Replace the tank temperature sensor if the signal still drops out with a known good harness connected