Powertrain, generic · Auxiliary emission controls

P040E EGR Temperature Sensor A Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

EGR temperature sensor A measures the gas temperature in the EGR path – for cooler monitoring, component protection and the EGR model. Whether it sits before or after the cooler depends on the maker: GM diesels have sensor A after and B before the cooler, Ford diesels sensor B after it. Like a coolant sensor it is an NTC, so a low voltage means hot. P040E means the signal jumps. GM diesels of 2016–18 set it when the measured resistance changes by more than 25 Ω between two samples 100 ms apart – faster than any real temperature change, so a loose contact or a cracked sensor is the cause (40 of 50 samples, MIL after two trips). Ford and GM's earlier Duramax LML do not use the code.

Likely causes

Loose contact in the connector or chafed wire
Sensor with an internal hairline crack
Corroded pins

Symptoms

  • Check engine light on, may come and go
  • No change in driving

Repair estimate

DifficultyEasyDIY possible
Parts and labour€50–250
Time0.5–1.5 h

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

Parts involved

egr temperature sensor aegr coolersensor wiringengine control module

Related codes

P040AP040BP040CP040DP041E

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.