Car Repair Help by Professional Mechanics
Diagnostic Testing /
Why is my service
engine soon light on?Why is My Car Service Engine Soon or Check
Engine Light On or
Flashing?
There is no mysterious reason your "service engine soon" illuminates on the instrument
cluster of your car. If you see a "check engine" or a "service engine soon" light
in your instrument cluster; your car has stored a
diagnostic trouble code.
Which
means the computer system on your vehicle has detected a problem within various
systems it controls. Your car has many different sensors that monitor the various
vehicle systems. If the trouble code light has been illuminated your vehicle enters
into "limp mode" this means it is running on a predetermined program that causes
poor mileage and increased emissions. An engine
trouble code reader is an easy to
use tool. All 1996 and newer vehicles utilize a "D" style plug-in connector that
connects to the
code reader.
On most vehicles the connector is located at the driver's compartment. Once the
code reader is plugged in you can retrieve trouble codes the engine computer has
stored in its memory. These codes are the same codes the dealer and repair shops
use to diagnose and repair your vehicle, as well as clearing the trouble codes
from the computers memory. An engine
trouble code reader is an easy
to use tool and is a worthwhile investment for future repairs
Service Engine Soon Light Scan for Trouble Codes Video
User Guide
1. Malfunction Indicator Lamp
The MIL has illuminated during driving this means there is a malfunction trouble
code stored in the vehicle's computer.
2. Locate Your Vehicle's Computer Connector
Locate your vehicle's computer connector (ALDL), most are on the lower driver's
side. In some vehicles you might need to look around a little, on the passenger's
side, and around the center console under a plastic cover. For more information,
check your owner's manual.
3. Connecting to The Computer to Read Codes
Connect your code reader to the under dash connector. The code reader will automatically
turn on and prompt you to the next step for code retrieval. Once the code has been
identified look up the identification on the trouble code chart supplied with your
code reader. After repair has been made clear trouble codes and recheck system.
After codes have been cleared the computer system is ready for internal testing,
this means that while the car or truck is in operation the onboard computer is performing
tests. These tests are called "monitors" most cars have between 4 and 8 monitor
systems. The computer goes through its testing procedure in about 40 to 60 miles.
Common Problems
- OBD2 (OBDII) Scan Test is Incomplete - The computer system or ECM, PCM (engine
control module, powertrain control module) that controls your car is equipped
with a basic operating program. This operating program is designed to control
your engine, transmission, emissions, safety systems and more. If a scan has
been performed by using a
code scanner
and a "scan could not be completed" code is retrieved further troubleshooting
is necessary. Usually a trouble
code P1000 or manufacturers equivalent. Will have listed several reasons
for this condition.
Stuck Engine Thermostat
- If the engine thermostat has stuck open it forces the engine coolant to
stay at too low of a temperature causing the ECM/PCM to
stay in open loop. This open loop creates a state of preprogrammed
parameters were no diagnostic tests can be preformed. (the ECM/PCM is
constantly waiting for the engine to heat up to operating temperature).
Shorted
Oxygen Sensor/Coolant Temperature Sensor - The ECM/PCM
relies on information from main sensors to operate,
if one of these sensors is severely shorted it can cause the ECM/PCM to stay
in open loop causing an incomplete systems check.
Shorted
Fuel Injector -If a fuel injector
short circuits it can cause the engine not to run by shorting the injector
driver in the ECM/PCM. This
in turn can cause incomplete code gathering which will result in a P1000
code.
- After a car repair has been performed the MIL indicator will illuminate
because the technician neglected to plug in a sensor.
- A blown fuse can cause the MIL to illuminate.
- A shorted sensor can cause the MIL to illuminate.
Diagnostic Testing /
Why is my service
engine soon light on?
Check Manufacturer Specific
Service Engine Soon Light Questions and Answers
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