What P0188 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 1, places it in the fuel and air metering subsystem; the last two digits identify the specific fault.
A fuel temperature sensor reports the temperature of fuel in the rail, pump or return line. Fuel density changes with temperature, so the engine computer uses it to correct injected quantity; on diesels and flex-fuel systems it is especially important.
The letter "B" distinguishes between two or more of the same component on one vehicle. Which physical part is "B" is set by the manufacturer, so confirm it in the service information before replacing anything.
What “Circuit High” means here
"High" means the signal or control voltage rose above the maximum the module expects. On a temperature sensor of this type (a thermistor fed from a 5 V reference through a resistor in the module), high signal voltage reads as a very low temperature, often the bottom of the scale. The usual explanations are an open circuit — an unplugged or corroded connector, a broken wire — or an open sensor.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0188:
- Often no noticeable symptom
- Hard hot starting on some engines
- Slight change in power or fuel use
Where to start diagnosing P0188
- On a cold-soaked vehicle the fuel temperature should read close to ambient.
- Inspect the connector and wiring; some sensors are combined with a fuel composition or pressure sensor.
- Compare the reading with an independent temperature measurement where accessible.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0188. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| Fuel temperature | There is no widely supported generic PID for it; most vehicles show it only in manufacturer-specific data. |
| Intake air temperature (PID 0x0F) | Cold-start comparison point. |
Related codes
Codes from the same fuel temperature sensor family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
| Code | Definition |
|---|---|
| P0181 | Fuel Temperature Sensor "A" Circuit Range/Performance |
| P0182 | Fuel Temperature Sensor "A" Circuit Low |
| P0183 | Fuel Temperature Sensor "A" Circuit High |
| P0184 | Fuel Temperature Sensor "A" Circuit Intermittent/Erratic |
| P0185 | Fuel Temperature Sensor "B" Circuit |
| P0186 | Fuel Temperature Sensor "B" Circuit Range/Performance |
| P0187 | Fuel Temperature Sensor "B" Circuit Low |
| P0189 | Fuel Temperature Sensor "B" Circuit Intermittent/Erratic |
Further reading
Frequently Asked Questions
What does P0188 mean?
P0188 is the generic SAE J2012 code for "Fuel Temperature Sensor "B" Circuit High". In plain terms, it means the engine computer has detected a "circuit high" fault on the fuel temperature sensor.
Can I keep driving with P0188?
Usually drivable with a substituted value, but have it diagnosed.
What should I check first for P0188?
On a cold-soaked vehicle the fuel temperature should read close to ambient.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.