The Volvo 940 (produced 1990–1998) uses a primitive but effective self-diagnostic system. Unlike modern OBD-II scanners, you typically read these codes using an LED blinker box located in the engine bay or by counting flashes from a built-in diagnostic unit.
1. Locating the Diagnostic System Depending on the model year, the Volvo 940 has one of two setups: A) The “Flasher Box” (1990–1995)
Location: Driver’s side strut tower (near the brake booster). Appearance: A small black box (approx. 2x3 inches) with a push button and an LED. Label: Usually marked “A” (for Engine) and “B” (for ABS, Cruise, etc.).
B) The OBD-I Port (1995–1998 - Late Models) felkoder volvo 940
Location: Same area, but instead of a box, you have a diagnostic socket (round or OBD-II shaped). Tool needed: You must build or buy a simple LED blinker with a jumper wire.
Note: 1995+ models in some markets (e.g., California) have OBD-II, but many still use the flash code method for engine diagnostics.
2. How to Read Fault Codes (Using the Blinker Box) For early models with built-in LED/button: The Volvo 940 (produced 1990–1998) uses a primitive
Turn ignition ON (do not start engine). Press the button on the diagnostic unit for 1 second . Watch the LED. It will flash a sequence of 3-digit codes .
Example: 1-2-1 (short pause between digits, longer pause between cycles).
Write down all codes. The system repeats after finishing. Locating the Diagnostic System Depending on the model
For late models with only a socket:
Connect an LED (with a 330–500 ohm resistor) between pin 3 (signal) and ground. Jump pin 3 to ground for 1 second. Count LED flashes as above.