P242B code meaning
Exhaust Gas Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 3)
Powertrain system Generic code P24xx codes Check engine light
What P242B means
P242B flags a reading from exhaust temperature sensor 3 on bank 1 that is electrically fine but makes no physical sense. Most checks start from a cold soak: GM's 3.0 L LZO (25OBDG04B) waits for more than 10,800 s engine-off and then expects the probe to warm up enough, which exposes a probe that has slipped from the gas stream or is frozen at one value (Type B). Ford's 2023 diesels want every probe within 50 °C of the others after 6 h off; VW's 2014 Touareg TDI compares sensor 3 with four other temperatures (60 K) and with its model (100 K). Not every case is a part fault: Volvo and Mack traced P242B on 2015–2016 trucks to a miscalculated soak time and issued software, and Jaguar found the DPF probe of the AJ20-D4 diesel loose or out of place. Jumpy signals go to P242E.
P242B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P242B
- MIL on, often together with P2080 or P2084
- No DEF dosing or parked regeneration refused
- DPF warning lamp on
Common causes of P242B
- Most likelySensor loose or no longer reaching into the exhaust stream
- PossibleSensor drifted or stuck at one value
- PossibleECM software miscalculating soak time (Volvo/Mack 2015–2016, software update)
- Less likelySensors swapped or wrong part fitted after repair
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Egt sensor b1s3
What each part of P242B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 2B | The exact fault in that area. |
What to do next
- Note P242B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P242B
What does P242B mean?
P242B means "Exhaust Gas Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 3)". P242B flags a reading from exhaust temperature sensor 3 on bank 1 that is electrically fine but makes no physical sense. It is a generic code, so it means the same on every make.
Is it safe to drive with P242B?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P242B fail an emissions test?
Yes, it can. P242B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P242B to fix?
Difficulty: medium. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P242B clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.