Upgrading a Classic Saab with a 3-Blink Turn Signal Switch

Bernie Saabman has 1999 Saab 9–5, which is considered a classic among certain car enthusiasts. The 9–5 was an executive sedan that combined high-end appointments with sporty handling. But, it lacked the 3-blink lane change indicator that many modern cars have. That’s a handy feature, because it allows drivers to quickly tap the turn signal stalk in situations where the signal doesn’t need to stay on. Saabman wanted that in his car, so he hacked it to add the feature.

Hacking a car’s computer system is a lot more complicated than the modifications most gearheads are willing to perform, such as bolting on a cold air intake. Beginning in the 1980s, manufacturers began increasing the levels of computerization in their cars, which improved efficiency, performance, and safety. The downside was that modifications to the computer system are difficult, and manufacturers have never really published schematics or protocol information — forcing owners to reverse-engineer and hack the systems.

In the case of a Saab from the late ’90s, that means hacking the DICE (Dashboard Integrated Central Electronics), which controls non-essential functions like the lights, air conditioning, and turn signals. Saabman used an Arduino Pro Micro to tap into the DICE’s multiplexer, in order to send custom turn signal commands. There are inputs for both the right and left blinkers, as well as pins for +5V and 0V, so Saabman’s code connects them to activate the turn signals three times before turning off.