P25D8: Fuel Level Sensor C Performance

P25D8 says that the third fuel level input delivers an electrically valid signal whose behaviour is not believable: it jumps, drifts or disagrees with the fuel actually used or transferred. A sender frozen at one value has its own code, P25DC, so P25D8 covers the remaining plausibility faults. No manufacturer documents P25D8 publicly. Comparable checks exist for the second sender: Ford treats more than 100 changes of over 40 % between samples taken every 0.1 s as a noisy signal (P2066), and GM's 2020 dual-tank logic checks whether the secondary sender reacts when its transfer pump moves fuel. A C-side check would likely follow similar ideas. CARB requires such rationality monitoring for fuel level inputs. The driver may see an erratic gauge or a range estimate that makes no sense.

Symptoms

• Fuel gauge jumps or shows unrealistic values
• Range estimate inconsistent
• Check engine lamp on after repeated detection

Most likely causes

• Worn or dirty resistor track in sender C giving jumps
• Transfer pump or line fault so the level in tank C does not change as expected
• Damaged or loose float on sender C

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the connector and wiring
2. Compare the reading with other engine data while varying the engine speed.
3. Use live data to compare the reading with actual conditions
4. Measure power, ground, and signal
5. Replace the sensor if the circuit is good

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P25D8 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 5: Speed and idle
• D8: Specific fault in that system

Frequently asked questions

Can I keep driving with code P25D8?

You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

What causes code P25D8?

The most common causes are: worn or dirty resistor track in sender C giving jumps; transfer pump or line fault so the level in tank C does not change as expected; damaged or loose float on sender C.

Related codes

• P25D7Fuel Level Sensor C Circuit
• P25DCFuel Level Sensor C Stuck
• P2066Fuel Level Sensor B Performance
• P0461Fuel Level Sensor A Circuit Range/Performance

Sources

• law.cornell.edu: 13 CCR 1968.2
• fordservicecontent.com: OBDSM2400OUTPUT 16Jul2024 WSM final V2 MCS7001
• gsi.ext.gm.com: 20OBDG04 Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.