ignition.tex

\documentclass[tikz]{standalone}
\usepackage{tikz}
\begin{document}
\tikzstyle{startstop} = [rectangle, rounded corners, minimum width=3cm, minimum height=1cm,text centered, draw=black, fill=red!30]
\tikzstyle{io} = [trapezium, trapezium left angle=70, trapezium right angle=110, minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=blue!30]
\tikzstyle{process} = [rectangle, minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=orange!30]
\tikzstyle{decision} = [diamond, minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=green!30]
\begin{tikzpicture}
\node (idlenormal) [small] {Select};
\node (idle) [process, above left= of idlenormal] {Idle};
\node (normal) [process,above right= of idlenormal] {Normal};
\node (add1) [small,below=of idlenormal] {$+$};
\node (catenable) [small,left=of add1] {On/off};
\node (cat) [process,left=of catenable] {Cat heatup};
\node (add2) [small,below=of add1] {$+$};
\node (temp) [process,left=of add2] {Temperature};
\node (select) [small,below=of add2] {Select};
\node (knock) [process,right=of add2] {Knock detection};
\node (startup) [process,left=of select] {Startup ignition};
\node (output) [startstop,below=of select] {Ignition angle};

\draw (idle) [-latex',thick] -- (idlenormal);
\draw (normal) [-latex',thick] -- (idlenormal);
\draw (cat) [-latex',thick] -- (catenable);
\draw (idlenormal) [-latex',thick] -- (add1);
\draw (add1) [-latex',thick] -- (add2);
\draw (catenable) [-latex',thick] -- (add1);
\draw (add2) [-latex',thick] -- (select);
\draw (temp) [-latex',thick] -- (add2);
\draw (knock) [-latex',thick] -- (add2);
\draw (startup) [-latex',thick] -- (select);
\draw (select) [-latex',thick] -- (output);
\end{tikzpicture}

\end{document}