MCI SERVICE INFORMATION

 

Engine Fast Idle - E4500 (Renaissance®)

Harness rework has been done on many older Renaissance coaches. It appears that one of the reworks may cause a problem with the fast idle. This problem occurs only when the coach has been driven in rainy weather. Under this condition, when the engine is running at fast idle, it remains in fast idle even after the fast idle switch is turned off. This can cause the transmission to remain in neutral when "Drive" is selected because the input shaft speed is too high. The remedy is simple to do and takes only a few minutes.

On the starter side of the engine is a harness that connects to the engine control module (ECM) and routes up to the RH engine compartment light bracket. On this bracket are two bulkhead connectors, labeled P-50 and P-36. On the engine side of P-36 are seven spare wires. These spare wires are normally tied back to the harness with electrical tape. On harnesses that have been reworked, they are all grouped together in a large piece of heat shrink tubing. In rainy weather, this tubing may catch and hold moisture around the ends of the spare wires. These wires are connected to the engine computer, and moisture may allow current to flow between them. Circuit 510 is one of the spare wires, and if the ECM senses voltage on it, the engine stays at fast idle.

Viewed from RH rear service door. On wheelchair-equipped coaches, from the access panel behind the wheelchair lift.

To remedy this, remove the heat shrink "boot", trim each wire ¼", and install adhesive heat shrink tubing on each individual wire. Install the tubing so it extends past the wire end by about ¼", and shrink using a heat gun. This will seal the wire end to prevent moisture from affecting engine performance. Secure the wires to the harness loom with electrical tape.

Motor Coach Industries - A New Flyer company: Corporate Address 200 East Oakton Street, Des Plaines, Illinois 60018 | Phone: 866-MCICOACH

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