Code Definition

P1909 — No signal from Engine Control Module 1

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Audi

About P1909

P1909 is a manufacturer-specific powertrain diagnostic trouble code recorded for Audi vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1909 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

DTC P1909 is set when the second engine control module (ECM 2) or the gateway detects that it is receiving no signal at all from Engine Control Module 1. On the Audi models that use two engine control modules to run a large engine, the modules depend on a constant data link, so if ECM 1 stops transmitting, its partner and the rest of the network lose the information they need. This usually points to ECM 1 being unpowered, held in reset, disconnected from the bus, or internally failed rather than simply out of sync. The vehicle will typically run in a reduced power or limp mode, may crank witho...

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