Powertrain, generic (extended)

P2494 EGR Cooler Bypass Position Sensor Circuit Low (Bank 1)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2494 is set when the raw voltage of the bank 1 bypass position sensor drops toward zero. GM documents it for the Duramax diesel: in the 2017 tables the signal must be below 1 % of the 5 V reference in 200 of 250 samples, checked every 6.25 ms once cranking is over and the powertrain relay supplies more than 11 V. The 2018 tables keep the test and the Type B rating, so the lamp comes on after two trips. GM groups P2494 with P2495 and P24C4 in one sensor fault bundle, which makes the bypass control fall back to a default. A signal near zero points to a short to ground, a missing 5 V supply or a broken signal wire pulled down inside the controller. High voltage is P2495; on bank 2 the low case is P2499.

Likely causes

Signal wire shorted to ground
Open 5 V reference wire to the sensor
Internal sensor fault in the bypass valve

Symptoms

  • Check engine light after two trips
  • Bypass control falls back to a default position

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–800
Time0.5–3 h

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

Parts involved

egr cooler bypass position sensor b1

Related codes

P2492P2493P2495P2499P24C4

References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.