P242B: 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. 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.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.

Symptoms

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the soot load and differential pressure with a scanner
2. Compare the reading with other engine data while varying the engine speed.
3. Check the differential pressure sensor's hoses
4. Check the temperatures before and after the filter
5. Fix any fuel injection or EGR codes before regenerating
6. Perform a regeneration while driving or at a repair shop when the diagnosis allows it

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P242B means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 4: Emissions
• 2B: Specific fault in that system

Frequently asked questions

Can I keep driving with code P242B?

If the light is on steadily, take a highway drive or go to a repair shop soon. If the car is in limp mode or the light is flashing, do not push the engine.

What causes code P242B?

The most common causes are: 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).

Related codes

• P242AExhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 3)
• P242CExhaust Gas Temperature Sensor Circuit Low (Bank 1 Sensor 3)
• P242DExhaust Gas Temperature Sensor Circuit High (Bank 1 Sensor 3)
• P242EExhaust Gas Temperature Sensor Circuit Intermittent/Erratic (Bank 1 Sensor 3)
• P2080Exhaust Gas Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 1)
• P2084Exhaust Gas Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 2)
• P20E3Exhaust Gas Temperature Sensor 1/3 Correlation (Bank 1)
• P20E4Exhaust Gas Temperature Sensor 2/3 Correlation (Bank 1)

Sources

• gsi.ext.gm.com: 25OBDG04B
• fordservicecontent.com: obd summary diesel 2023
• static.nhtsa.gov: MC 10074008 2280
• static.nhtsa.gov: MC 10133245 9999

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.