Powertrain, generic (extended)

P242B Exhaust Gas Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 3)

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

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.

Likely causes

Sensor loose or no longer reaching into the exhaust stream

Sensor drifted or stuck at one value

ECM software miscalculating soak time (Volvo/Mack 2015–2016, software update)

Sensors swapped or wrong part fitted after repair

Symptoms

MIL on, often together with P2080 or P2084
No DEF dosing or parked regeneration refused
DPF warning lamp on

Repair estimate

DifficultyMediumDIY possible

Parts and labour€0–350

Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

egt sensor b1s3

References: gsi.ext.gm.com, fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov.