PINPOINT TEST DP: Powertrain Control Module (PCM) Vehicle Speed: Notes

WARNING: This vehicle is equipped with high voltage cables, components, and wiring. The high voltage warning labels containing the high voltage symbol are located on each high voltage component. High voltage cables and wiring are orange in color. Certified rubber insulating gloves and a face shield must be worn when working with the high voltage cables, components, or wiring. The ignition key must be cycled to the OFF position for a minimum of 5 minutes, and the high voltage traction battery service disconnect plug placed in the servicing/shipping position before disconnecting the high voltage cables. Failure to follow these instructions may result in personal injury or death.
Do not disconnect, disable, or touch the high voltage cables, components, or wiring during the module reprogramming procedure because high voltage is present. The high voltage warning labels containing the high voltage symbol are located on each high voltage component. High voltage cables and wiring are orange in color. Failure to follow these instructions may result in personal injury or death.

Important Safety Notice

Appropriate repair methods and procedures are essential for the safe, reliable operation of all motor vehicles, as well as the personal safety of the individual doing the work. This service information provides general directions for repairing vehicles with tested, effective techniques. Following them helps to establish reliability. There are numerous variations in procedures, techniques, tools, and parts for repairing vehicles, as well as in the skill of the individual doing the work. This service information cannot possibly anticipate all such variations and provide advice or cautions as to each. Accordingly, anyone who departs from the instructions provided in this information must first establish that they compromise neither their personal safety nor the vehicle integrity by their choice of methods, tools, or parts.

The Hybrid uses three methods to calculate vehicle speed:

from the anti-lock brake system (ABS); The ABS module calculates wheel speed from the front two wheel speed sensors and sends this information to the PCM through the communication network.
from the transaxle control module (TCM); The TCM calculates traction motor speed from the traction motor shaft speed sensor and combines it with (PCM stored) tire size and axle ratio data to determine vehicle speed. This calculation is then sent to the PCM over the communication network.
from the PCM engine speed and the TCM generator speed; The TCM calculates generator speed from the generator shaft speed sensor and sends this information to the PCM. The PCM combines input information from the generator speed and engine speed along with tire size and gear ratio to calculate a vehicle speed.

The PCM strategy then cross checks all the inputs to determine if they agree with one another. If there is a discrepancy between inputs, a vehicle speed fault flag is set in the PCM and a DTC is stored.

This pinpoint test is intended to determine which of the three vehicle speed inputs caused the PCM vehicle speed diagnostic trouble code (DTC).