9553 Mercruiser CYLINDER HEAD ASSEMBLY

Table 1
Revision Summary of Changes
01 Added a statement and note in the "Inspection of TOS Sensors" section. Introduction
The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.Problem
The transmission may experience an unintended downshift, which during elevated machine travel speeds, may result in a power train overspeed condition. A power train overspeed can cause resultant damage to the transmission, torque converter, engine, and other power train components. An unintended downshift can be caused by in-range failures of speed sensors or intermittent harness connection issues (fretting, corrosion, loose fasteners).Solution
Do not operate or work on this product unless you have read and understood the instruction and warnings in the relevant Operation and Maintenance Manuals and relevant service literature. Failure to follow the instructions or heed the warnings could result in injury or death. Proper care is your responsibility.
Note: The codes listed below in Table 2 are active when the truck has ground speed. Static electrical tests may appear to be compliant, yet intermittent errors can still exist. The event frequency (high count of events), duration (length of time), and operator feedback regarding the location of events can help aide in further defining what direction to take for proper troubleshooting steps. For intermittent type events, it is recommended to troubleshoot the sensor wiring within all speed and gear ranges for a length of time.Look for the symptoms (codes/events) listed in Table 2 below.
Table 2
TOS Sensor Codes (MID 81)
Machine Type Diagnostic Code (CID-FMI) Description
Standard 585-02 Transmission Output Speed Sensor #1 - Erratic, Intermittent, or Incorrect
Standard 585-08 Transmission Output Speed Sensor #1 - Abnormal Frequency, Pulse Width, or Period
Standard 673-02 Transmission Output Speed Sensor #2 - Erratic, Intermittent, or Incorrect
Standard 673-08 Transmission Output Speed Sensor #2 - Abnormal Frequency, Pulse Width, or Period
CMD 3792-02 Transmission Output Speed #1 Signal Line #1 - Erratic, Intermittent, or Incorrect
CMD 3792-08 Transmission Output Speed #1 Signal Line #1 - Abnormal Frequency, Pulse Width, or Period
CMD 3793-02 Transmission Output Speed #1 Signal Line #2 - Erratic, Intermittent, or Incorrect
CMD 3793-08 Transmission Output Speed #1 Signal Line #2 - Abnormal Frequency, Pulse Width, or Period
CMD 3794-02 Transmission Output Speed #2 Signal Line #1 - Erratic, Intermittent, or Incorrect
CMD 3794-08 Transmission Output Speed #2 Signal Line #1 - Abnormal Frequency, Pulse Width, or Period
CMD 3795-02 Transmission Output Speed #2 Signal Line #2 - Erratic, Intermittent, or Incorrect
CMD 3795-08 Transmission Output Speed #2 Signal Line #2 - Abnormal Frequency, Pulse Width, or Period
Table 3
TOS Sensor Event Codes for the Transmission ECM
Machine Type EID Level Description Possible Cause and Recommended Response
CMD 330 3 Transmission Output Speed Mismatch Immediate safe shutdown is required. Perform speed sensor component test (inspect wiring harness, replace speed sensor). Both TOS sensor wires lead through same machine harness connectors. Connection issues can affect one or both TOS sensor signals to ECM. Proceed to Inspection of Harness.Inspection of TOS Sensors
Inspection is needed especially on the following machines:
Recently serviced/assembled machines.
Machines that have had frequent water ingress/high-pressure washing.Note: Most prevalent on all 793F RBT & RB4 factory CMD ready, 797F LAJ & LTZ, 793F SSP & SND, and 789D SPD converted to AHS assets. However, any models experiencing the following errors need to fix the sensors or wiring.See Illustrations 1 through 19 for visuals of harness connection points, misassembled harnesses, and corrosion.When inspecting the speed sensors ensure block retention 6V-5696 Bolt is secured with loctite and torqued to spec. Refer to Illustration 1.Note: The Slip ring is designed to have minimal movement when the bolt and bl