Computer System Service 19. Computer System Service

by Russell Krick Publisher The Goodheart-Willcox Co., Inc Tinley Park, Illinois Permission granted to reproduce for educational use only Permission granted to reproduce for educational use only  Preliminary visual inspection  Computer system circuit problems  Sensor and actuator problems  Sensor service  Actuator service  Computer service Permission granted to reproduce for educational use only  Involves looking for signs of obvious trouble:  loose wires, leaking vacuum hoses, damaged parts, etc  When a computer system malfunction occurs, the cause is often something simple Permission granted to reproduce for educational use only Contaminated Engine Oil  Something as simple as contaminated oil can set a trouble code  Fumes from the crankcase are drawn into the intake manifold for burning  these fuel-rich vapors can trick the oxygen sensor into signaling a rich airfuel mixture, setting a trouble code Permission granted to reproduce for educational use only Contaminated Engine Oil Permission granted to reproduce for educational use only Electrical Component Damage  Semiconductor devices are very easily damaged by static electricity, voltage spikes, heat, and impact shocks  Here are some rules to remember when working with electronic devices and their wiring:  Arc welding can damage on-board computers Permission granted to reproduce for educational use only Electrical Component Damage  Never disconnect the battery cables while the engine is running  Do not disconnect or connect wiring, especially the computer wiring, with the ignition on  Make sure you not reverse the battery cable connections Permission granted to reproduce for educational use only Electrical Component Damage  Wear an anti-static wrist strap whenever you handle static-sensitive components  Only use high impedance test lights and meters when checking electronic circuits or their wiring  Do not disconnect a scan tool from the data link connector with the ignition on Permission granted to reproduce for educational use only  Most electrical-electronic problems are actually basic circuit problems  increased or decreased current, resistance, or voltage Permission granted to reproduce for educational use only PROM Service  Many computers use a PROM to store data for the specific vehicle make and model  Remove the cover over the PROM  Using a PROM tool, remove the PROM from the old computer  Do not touch the PROM terminals Permission granted to reproduce for educational use only PROM Service  Before installing the PROM in the computer, use a blunt tool to push the chip into the carrier  Make sure the reference marks are positioned properly so the PROM is not installed backward  Touching only the carrier, position the PROM pins into the socket in the computer  Install the cover over the PROM Permission granted to reproduce for educational use only PROM Service Permission granted to reproduce for educational use only Updated PROM  Modified integrated circuit used to correct a driveability problem or improve a vehicle’s performance  Produced to correct problems such as surging, extended cranking periods, excessive emissions, etc Permission granted to reproduce for educational use only EEPROM Programming  Electrically Erasable Programmable Read Only Memory (EEPROM)  Permanently soldered to the circuit board  Often reprogrammed to correct driveability and performance problems Permission granted to reproduce for educational use only EEPROM Programming  Programmed using a method called flash programming  There are three methods used to program an EEPROM:  direct programming  indirect programming  remote programming Permission granted to reproduce for educational use only Direct Programming  Fast and simple method of programming  New information is downloaded by a shop computer directly to the data link connector Permission granted to reproduce for educational use only Indirect Programming  Vehicle information is downloaded from a programming computer into the scan tool  Information is then downloaded from the scan tool into the vehicle’s computer Permission granted to reproduce for educational use only Remote Programming  Done with the vehicle’s computer removed from the vehicle  Used when changes need to be made through a direct modem connection to a manufacturer’s database computer  Done only at new vehicle dealerships Permission granted to reproduce for educational use only EEPROM Programming Procedure  Make sure that the battery is fully charged  Connect the programming computer or scan tool to the data link connector  The computer or scan tool may ask you to enter the engine and vehicle type, as well as the VIN  Go to the programming software and follow the prompts Permission granted to reproduce for educational use only Programming a New Computer  If a new computer is being installed, program only that computer  Never attempt to program a new computer with information from the old computer  An erasure may need to be performed on a new computer before initial programming can take place Permission granted to reproduce for educational use only Reprogramming Computers  Determine the date that the current programming was downloaded or check the program’s calibration number  If the latest program has not been downloaded, proceed with the reprogramming sequence Permission granted to reproduce for educational use only Reprogramming Computers  If necessary, erase the existing information from the computer  Select the updated calibration from the programming computer or scan tool menu  Download the new information into the computer Permission granted to reproduce for educational use only Reprogramming Computers  Monitor the reprogramming progress to determine when it is complete  When programming is complete, turn the ignition switch to the position called for in the program  Disconnect the computer or scan tool  Verify the vehicle operation Permission granted to reproduce for educational use only Computer Relearn Procedures  After being serviced, the computer system may have to go through a relearn procedure  period of operation during which the computer adapts to new components and programming information  Driving the vehicle for a short time can usually restore idle quality and driveability  Some scan tools may offer a forced relearn procedure Permission granted to reproduce for educational use only