We show that the weak detonation waves for a combustion model of Rosales-Ma
jda are nonlinearly stable. Because of the strongly nonlinear nature of the
wave, usual stability analysis of weakly nonlinear nature does not apply.
The chemical switch on-off is the main feature of nonlinearity. In particul
ar, the propagation of the wave depends sensitively on the tail behaviour o
f the flow in front of it. Unlike the strong detonation waves, a weak deton
ation is supersonic and there is the separation of the gas waves from the r
eacting front. As a consequence, the reacting front needs to be traced.