Powertrain, generic (extended)

P242C Exhaust Gas Temperature Sensor Circuit Low (Bank 1 Sensor 3)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P242C means the signal of exhaust temperature sensor 3 on bank 1 sits below its valid range. What that says about the wiring depends on the sensor type. GM's 2020 diesel tables (20OBDG04) read a resistance under 158 Ω as a grounded circuit and need 10 bad samples in a window of 20 (Type B); on the 3.0 L LZO a digital thermocouple module reporting below -72.8 °C counts the same way, with 19 of 25 samples. Ford's 2023 diesels use a voltage floor of 0.10 V, VW's 2014 Touareg TDI 0.68 V. Deutz describes P242C-00 as a grounded signal on the probe behind the SCR catalyst. A harness chafed through near the hot exhaust or a crushed connector is the usual find. The ECM then works with a substitute value and normally holds back regeneration.

Likely causes

Signal wire chafed and shorted to ground near the exhaust
Connector damaged, wet or with pushed-back terminals
Sensor shorted internally

Symptoms

  • MIL on after the second faulty trip on GM
  • Sensor 3 shows an implausibly low temperature in the scan tool
  • Regeneration blocked, filter load rising

Repair estimate

DifficultyMediumDIY possible
Parts and labour€40–350
Time0.3–1.5 h

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

Parts involved

egt sensor b1s3

Related codes

P242AP242BP242DP2032P2468

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