Summary form only given. In wireless mobile ad hoc networks (MANET), energy is a scarce resource. Though cooperation is the basis of network services, due to the limited energy reserve of each node, there is no guarantee any given protocols would be followed by nodes managed by different authorities. Instead of treating the selfish nodes as a security concern and trying to eliminate them, we propose a novel way to encourage cooperative works - rewarding service providers according to their contributions. Nodes in a MANET can form coalitions to reduce aggregate transmission power on each hop along a route. The payment of each node in a coalition is determined by using Shapley Value, a well-known concept in game theory for allocating payoff for each member in a cooperative coalition. We present the contribution reward routing protocol with Shapley Value (CAP-SV). It achieves the objective of truthfulness. The performance of CAP-SV is studied by simulations using ns-2. Analysis and experimental results show a routing protocol with the consideration of the incentives of individual nodes stimulates cooperation and improves network lifetime without significantly diminishing the performance of the whole network.