The recent frigid temperatures are a reminder that winter is far from over. Fortunately, you can rely on your Thomas Saf-T-Liner C2 buses equipped with Cummins engines to start during extremely cold temperatures, with proper maintenance. Here’s a cold weather tip to help your bus drivers make things easier for your service technicians.
Wait To Start
Under cold starting conditions, when the key is turned to the ON position, a WAIT TO START light illuminates on the dash. This light will stay on for a brief period – from a few seconds up to 30 seconds. It’s vitally important that drivers wait for the WAIT TO START light to go off before cranking the bus. Failing to do so can result in a check engine light with a number of possible fault codes.
To prevent this and other possible service issues, have your drivers remember these three simple rules:
- Turn the key to ON.
- Wait until the WAIT TO START light goes off.
- Start the bus.
Under the Hood: A Brief Explanation of What’s Happening and Why
While it’s a simple procedure, observing the WAIT TO START light serves a very important function. The Saf-T-Liner C2’s Cummins engine is equipped with a grid heater inside its air system. This grid heater takes a few seconds to heat up and has three purposes:
- Assists the engine’s cold weather start-ability by preheating the intake air
- Helps control white smoke during cold starting (reduced hydrocarbon emissions – EPA requirement)
- Performs a post-heat cycle that helps remove carbon from the grid heater element (EPA requirement)
Drivers need to wait for the WAIT TO START light to go off before cranking the bus. This waiting period allows the grid heater to do its job. The length of time the WAIT TO START light stays on depends on the ambient temperature. The lower the ambient temperature, the longer the light will stay on.
If the bus is cranked before the WAIT TO START light goes out, the Engine Control Module (ECM) may set one of several possible fault codes:
- 3555 – Abnormal update rate
- 3556 – Received network data in error
- 4252 – Condition exist
Turn – Wait – Start
This simple three-step rule is an easy way to help your drivers remember this important cold weather tip for the benefit of your service technicians.
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