P2494 code meaning
EGR Cooler Bypass Position Sensor Circuit Low (Bank 1)
Powertrain system Generic code P24xx codes Check engine light
What P2494 means
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.
P2494 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P2494
- Check engine light after two trips
- Bypass control falls back to a default position
Common causes of P2494
- Most likelySignal wire shorted to ground
- PossibleOpen 5 V reference wire to the sensor
- PossibleInternal sensor fault in the bypass valve
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EGR cooler bypass position sensor b1
What each part of P2494 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 94 | The exact fault in that area. |
What to do next
- Note P2494 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2494
What does P2494 mean?
P2494 means "EGR Cooler Bypass Position Sensor Circuit Low (Bank 1)". P2494 is set when the raw voltage of the bank 1 bypass position sensor drops toward zero. It is a generic code, so it means the same on every make.
Is it safe to drive with P2494?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2494 fail an emissions test?
Yes, it can. P2494 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2494 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P2494 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.