P0188: The fuel temperature sensor B signal is higher in voltage than the computer expects, which it reads as unusually cold fuel
Fuel temperature sensor B circuit high
Severity: Severity not verified — if the car runs badly, have it inspected
No source we read says how urgent this code is, so we have not set a severity; have it read and checked rather than assuming it is harmless.
P0188 in short
P0188 means the fuel temperature sensor B circuit is sending a higher voltage than the engine computer expects, which it reads as unusually cold fuel. A faulty sensor, an open or shorted wire, or a corroded connector are the usual causes. Hard starting is possible.
The fuel temperature sensor tells the computer how warm the fuel is so it can correct fuel delivery. Sensor B is the second sensor on engines that have more than one.
TroubleCodes.net says the code sets when the signal voltage rises above the calibrated limit, which the computer reads as lower than normal temperature.
The Delaware DMV list gives the same title (fuel temperature sensor B circuit high input), so both sources agree on the meaning.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Open or shorted wiring, or water or corrosion in the harness
Common general cause- Why it ranks here
- TroubleCodes.net lists open or shorted circuits, water entry and damaged harnesses first.
- What would change this
- Resistance or continuity faults found by flexing the harness raise it.
Cause 2: Faulty fuel temperature sensor
Common general cause- Why it ranks here
- The sensor itself is listed as a cause.
- What would change this
- Sensor resistance outside the repair manual's spec raises it.
Cause 3: Engine computer fault or excess voltage in the system
Possible — needs testing- Why it ranks here
- The page also lists a defective computer, or an alternator producing excess voltage, as possible causes.
- What would change this
- Considered only after the sensor and wiring pass.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Inspect the computer connector pins and the sensor connector for corrosion or water, and flex the harness to see whether the fault changes.
IfCorrosion, water or a damaged wire is found
It meansRepair the connector or wiring.
Points to: Open or shorted wiring, or water or corrosion in the harness
IfNo damage is found
It meansTest the sensor.
Step 2: Measure the sensor's resistance and compare it with the repair manual; check for the 5 V reference at the connector with the key on.
Warning:Probing a live connector can short pins and damage the computer; use proper back-probes.
IfResistance is out of spec
It meansReplace the sensor.
IfThe reference voltage is missing or wrong
It meansTrace the circuit back to the computer.
Points to: Engine computer fault or excess voltage in the system
Symptoms
- Check engine light
- Poor fuel economy
- Possible hard starting and poor performance
How to fix
Step 1: With the ignition off, check the fuel temperature sensor connector and wiring for corrosion or damage.
On your vehicle
We don't have reviewed vehicle-specific evidence for P0188 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P0188 yet.
P0188 questions
What does P0188 mean?
The fuel temperature sensor B circuit is sending a higher voltage than expected, which the computer reads as unusually cold fuel.
Sources and review
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error