 | ||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||
|
On 1991-1993 Buick Park Avenue Problem Can Be Defective Crankshaft Sensor Or Connection Between Sensor, Ignition ModulePosted 2/12/2000By Dave Martin
Timing Chain Can Cause Coolant Leak in Engine Oil
Vehicle: 1991 through 1993 Buick Park Avenue. 3800 VIN L. If the 3X signal from the crankshaft sensor fails while running, the engine will continue to run but the module will not send out the spark reference signal. The PCM will set a code 17 when this occurs. Test and quick fix: To check the circuit, monitor the 3X signal at the light blue/white wire, terminal H at the module, with the engine running. It should be a square wave. At idle, this signal measures about 40 Hz. If this signal stops, the SES light turns on within several seconds and sets a code 17. Repair the wiring or replace the crankshaft sensor. Background: Code 17 indicates that the PCM has received 240 fuel control pulses since the last spark reference pulse. The spark reference pulse is used by the PCM to improve ignition timing accuracy below 1200 rpm and to allow computer control (EST) of timing during cranking. This reduces emissions and allows for better low speed engine performance. The MIL is not illuminated for this code. Normal diagnostics may not include the possibility of the 3X signal failing after start-up. If the normal diagnostics fail to fix the problem, start the engine and monitor the 3X crank sensor signal at the module. Using a lab scope, the 3X signal is typically a 0 to 7 (or 0 to 5) volt square wave. The module sends out an approximate 7 (or 5) volt reference signal to the crank sensor and the crank sensor pulls it down to 0 volts when a vane passes by the crank sensors hall effect circuit. The "on" time of the signal is either 10, 20, or 30 degrees of crankshaft rotation, depending on which vane is passing through the hall effect. If the signal breaks up or quits, verify that all wiring is OK. If it is, replace the crankshaft sensor. Make sure the vanes are not magnetized- they may distort the signal to the point that the module may not recognize it. To understand how this code is set, it is essential to understand the relationship between the various signals sent and received by the module. During cranking, at a minimum, the module must receive both the 3X and the 18X signals from the crank sensor. These signals are needed by the module to start the correct coil firing sequence and to generate the initial fuel control pulse (circuit 430) used by the PCM to fire the injectors. If the 3X signal fails while the engine is running, the engine will continue to run on the 18X signal alone. The module remembers the coil firing sequence and will continue to send a fuel control pulse to the PCM; however, the module handles the spark reference pulse in a different manner. If the 3X signal fails while the engine is running, the module will discontinue the spark reference pulse to the PCM. This pulse is not generated by the module unless both crank signals are active.
|
|||||||||||||||||||||||||||||||||
Copyright (c) 1996-2008. Automotive Service Association. All rights reserved.
 | ||||||||||||||||||||||||||||||||||
This information is provided by IDENTIFIX®. IDENTIFIX® resources cut diagnostic time and provide repair solutions that increase the shop's bottom line. From Repair-Trac pattern failure quick fixes, to Diagram-Online wiring diagrams by fax, to the Repair Hotline staffed by 32 master techs who specialize in diagnosing complex problems by phone or fax, IDENTIFIX® helps techicians fix more cars in less time.
