Based on empirical data, we present an intervention to promote collaborative diagnostic problem solving in automotive technician trainees. The intervention focuses on teaching a strategy for collaborative diagnostic problem solving in combination with worked examples and varying degrees of guided self-explanation tasks. Results from a pilot study of 8 dyads indicate that the intervention promoted the exchange of relevant content in the process. Solution examples increased learning efficacy and reduced trainees' perceived cognitive load. Differences between strongly and weakly guided self-explanation tasks did not appear. Longer-term effects on the process need to be assessed in follow-up studies.