SERVICE MANUAL UPDATE SEC. 8A REVISED TWO FLOW ELECT. STG.
Subject: SERVICE MANUAL UPDATE - SECTION 8A REVISED, TWO FLOW ELECTRONIC STEERING
Models Affected: 1992 BONNEVILLE SE MODELS
The following: TWO FLOW ELECTRONIC (TFE) STEERING (T2V) with sport package (W21) schematics and diagnostics found in Section 8A-45-0; 8A-45-1; 8A-45-2; and 8A-45-3 of your service manual, have been revised with more thorough and accurate diagnostics.
Please update your service manual accordingly.
WITH SPORT PACKAGE (W21)
COMPONENT LOCATION
Item....................... Description..........................Figure -------------------------------------------------------------------------- Multi-Function Chime ......Behind center of I/P, right of (MFC) Module steering column support...............201- 9-D
Powertrain Control ....... Behind RH side of I/P, Module (PCM). near shroud........................ . 201- 10-A
Relay Center.............. Behind RH side of I/P, top of RH shroud..................... ... 201- 10-A
TFE Steering Solenoid..... Lower RH rear of engine, above oil filter.................. .. 201- 0-C
C260 (56 cavities).........Behind RH side of I/P, near dash to engine grommet P102... . 201- 5-B
P102.................... RH rear of engine compartment, behind strut tower................. 201- 5-A
S173 ......... ...........Engine harness, RH rear of engine.... 201- 0-A
S256 ............... ....Composite harness, behind RH side of I/P, near shroud.............. 201- 8-B
TROUBLESHOOTING HINTS
o Try the following checks before doing the System Check.
1. Check Relay Center Fuse 5 by visual inspection.
SYSTEM CHECK
o Use the System Check Table as a guide to normal operation. o Refer to System Diagnosis for a list of symptoms and diagnostic steps.
SYSTEM CHECK TABLE
ACTION NORMAL RESULTS ----------------- ------------------- With Ignition Wheels turn right, Switch in RUN, then left with turn steering wheel minimal effort to the right, then to the left
Wait 3 minutes while Greater effort needed leaving Ignition Switch to turn wheels right in RUN, and repeat then left above action
o Refer to System Diagnosis when a result is not normal.
SYSTEM DIAGNOSIS
o Do the tests listed for your symptom in the Symptom Table. o Tests follow the Symptom Table.
SYMPTOM TABLE
SYMPTOM FOR DIAGNOSIS ---------------- -------------- Increased steering Do Test A effort at low speeds
Steering effort does not increase at speeds Do Test B above 32 km/h (20 mph)
WITH SPORT PACKAGE (W21) CIRCUIT OPERATION
The Two Flow Electronic (TFE) Steering system increases power steering assistance while the vehicle travels at slow speeds. This allows for easier steering effort at slow speeds, and provides a more direct steering "feel" at high speeds.
The Multi-Function Chime (MFC) Module receives a vehicle speed signal from the Powertrain Control Module (PCM). The Multi-Function Chime (MFC) Module grounds terminal B8, energizing the TFE Steering Solenoid, when the ignition input (terminal A3) to the MFC Module is on and one of the following conditions are met:
o The vehicle is increasing in speed and the speed is between 0 and 20 mph.
o The vehicle is decreasing speed and the speed is less than 17 mph.
o The vehicle is not moving. The solenoid activation times out after 120 seconds if no speed pulse is received during this time.
Power steering assistance increases when the solenoid is energized to ease steering effort.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
