Tranny.

Yes, Champion bought the rights to make a special, way over priced plug that only the dealers sell. Most Double Platinum Champions or Bosh work great for $4 to $6 a piece.

 

The speed sensors are located near each wheel, and report to the slabs ecu which in turn reports vehicle speed to the engine management ecu for idle control and also for information it shares with the transmission ecu. The information is used for the speedometer and cruise control as well. Typically it does not directly affect engine speed outside of the cruise control function, but will suspend a misfire code signal if the individual speed sensors are reporting enough variation to suggest the road is bumpy.

Knowing your truck has the GEMS system, the following might shed some additional light on the problem.

Here is what the Bosch 5.2.1 manual indicates for the MAF sensor failure:

• The MIL lamp will be illuminated once the fault is "debounced" or is repeating and not a fluke.
• The engine speed might dip before the ecu introduces a default strategy (open loop or limp home).
• Engine may be difficult to start and prone to stalling.
• Throttle response will be adversely affected.
• Emissions will be out of tolerance.
• Idle will be rough and prone to stalling.

Perhaps the MAF is failing, but not repeatedly as is usually the case. If so, it may not illuminate the MIL.

 

He has a DI, this is not relevant to him.
The vehicle speed sensor is what tells the engine computer how fast you are going, it is also the speed limiter.
When it fails it sends a bad single to the ECU usually telling it that you are exceeding the trucks governed top speed (110mph) and then the ECU cuts fuel injectors to slow you down.

A bad VSS will NOT throw a check engine light and is very easy to mis diagnosis if you dont know the brand.

 

Spike,

how hard would it be for me to change the VSS myself? Is this something that can be done by a novice? And if so can you guys walk me through it if i can provide pictures?