ON CAR ELECTRICAL SYSTEMS
This blog will be an in depth focus on some of the components I covered in the 4848 on car electrical. I will be covering their intended uses, how they work and some of the things that go wrong with them. The primary focus will be on fuel injectors and various ways to scan the ECU for errors via a scan tool or flash codes. The components I will be covering are......
1)Fuel injectors 2)Scan tools 3)Flash codes
Fuel injectors
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| http://www.northamptonmotorsport.com/default.asp?id=95 |
Fuel injectors are used to deliver fuel into the combustion chamber of a vehicle. It is the most common type of fuel delivery system for diesel and petrol vehicles, and has almost completely replaced carburetors since the 1980s. This is primarily due to the fact that electronic fuel injection (EFI) can deliver and atomize fuel far more efficiently than a carburetor, which creates less pollution and better fuel economy (which saves money)
How does it work?
The injectors atomize the fuel by forcibly pumping the fuel out of a tiny nozzle under extreme pressure. When communicating with various sensors (MAF/MAP/TPS/02/Crank) the ECU can actuate the injectors at the precise moment, maximizing fuel efficiency while getting peak performance. EFI systems can react very quickly to changing inputs like sudden throttle movements.
This video explains how fuel injectors work
This video explains how fuel systems work in general
Problems with injectors
Injectors are subject to extreme heat and intense work loads. An average injector will cycle approximately 18,000,000 times a year. This coupled with the fact that an injector is a mechanical and electrical component, all injectors eventually fail (especially if its a high performance vehicle). The problems associated with injectors are
1...Unburned fuel additives are baked on the injector pintle and orifice altering flow volume, altering fuel spray pattern.
2...Injector filters become clogged.
3...Injector windings don't lift pintle, seized pintle, or slow pintle cycling.
4...Body or mechanical joint leak in injector body.
5...injector pintle doesn't fully seat on orifice.
6...external electrical connectors broke/corroded.
information gathered from http://www.jaguarfuelinjectorservice.com/WebStore/Fuel%20injector%20problems.htm
Testing fuel injectors
During the coarse of the year we did a few tests on injectors to see whether they were functioning properly or not. The engine I focused on was out of a Toyota 4A-FE corolla. The 3 common tests used to see whether an injector is working are....
1) Place a screwdriver on the injector and place it to your ear.
2) Back probe it with a pin, then use a volt meter or an oscilloscope.
3) Back probe it with a pin and hook up an LED/noid test light.
Step 1
Personally I would use a screwdriver first as it will immediately tell me If the injector is actuating. It should be making a sharp tapping sound. A dull thud would indicate a problem while no sound would indicate it wasn't working. If its making a dull thud the injector may need to be cleaned. If its making no sound check the wiring harness. If there's available voltage at the wires the injector is broken.
Step 2
Back probe the injector with pins and then check it with either a volt meter or an oscilloscope. Check the voltage reading of each injector. If one of them has a variation of more then 0.3v chances are its either faulty or the wiring harness is stuffed.
Step 3
Simply disconnect the injector plug from the injector . Hook this plug up to the LED/noid light. Start the vehicle. If the ECU and wiring harness are working fine it should begin to flash. If no light appears there is either a fault with the ECU or the wiring harness.
1) Place a screwdriver on the injector and place it to your ear.
2) Back probe it with a pin, then use a volt meter or an oscilloscope.
3) Back probe it with a pin and hook up an LED/noid test light.
Step 1
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| http://www.club3g.com/forum/problem-reports/106131-p0305.html |
Personally I would use a screwdriver first as it will immediately tell me If the injector is actuating. It should be making a sharp tapping sound. A dull thud would indicate a problem while no sound would indicate it wasn't working. If its making a dull thud the injector may need to be cleaned. If its making no sound check the wiring harness. If there's available voltage at the wires the injector is broken.
Step 2
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| http://www.vstrom.info/Smf/index.php?topic=7512.0 |
Step 3
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| http://www.popularmechanics.com/cars/how-to/repair-questions/4330138 |
Scan tools
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| http://www.denlorstools.com/home/dt1/page_16171_657/otc_3825_pegisys_automotive_diagnostic_scan_tool_o.html |
Scan tools are used to check, diagnose and sometimes reprogram a ECU. A scan tool is connected to the ECU via a data link connector (DLC). If a ECU is noticing some abnormalities it will put of a fault code. Older model vehicles may not be able to communicate with scan tools and communicate via flash codes instead, these will be covered in the next part of the blog. Scan tools come in all shapes and sizes and are made from many different manufacturers. They can take various readings and let you know how the various sensors are doing. They are usually able to work on a wide range of vehicles by choosing different manufactures like the picture listed above.
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| Picture of a scan tool showing the various sensors and the various voltage readings. If they are not reading at the appropriate range it would be listed as a fault. (http://www.j2534reprogrammer.com/bonus-gen2.html) |
This movie shows how scan tools are now capable of hooking up to a car and going wireless to your laptop. Not only that if your car ECU is sophisticated enough you even activate the actuators
Error codes
Error codes are messages sent by the ECU to the dashboard to let you know there is something wrong with your car. Even if you fix the problem in most cases you will need to clear the codes afterwards as the fault code will still stay on the dash. A vehicle we did a test on was a 1998 Mazda 323 manual sedan. After the tutor put in some fault codes (disconnected something in the engine bay) we hooked up the scan tool. A warning light popped up on the dash so we hooked up a scan tool. The scan tool read the following fault codes.
code number system affected Condition described
P0122 TPS (throttle position sensor) Circuit low input
P0133 IAT (intake air temperature sensor) Circuit high input
P0103 MAF/VAF (Mas airflow sensor) Circuit high input
Turns out he had simply disconnected the TPS and MAF sensor. After plugging them back in and resetting the fault codes the car was running fine. Because we used a scan tool we were able to locate the problem very quickly. This would save a customer time and money as finding faults without 1 can be very time consuming. Although they were rather simple repairs (he simply disconnected the sensors), in a work shop situation it could point to a number of problems. These symptoms could be anything from corroded/broken wires and connections to simply having a broken sensor. With a scan tool we can narrow down the cause without having to use an educated guess were the problem is.
Problems with scan tools?
Although scan tools are pretty efficient they weren't always so. When they first came out they were tedious to
use and very expensive. This made them very unpopular with local garages. Some of the common problems are listed below.
use and very expensive. This made them very unpopular with local garages. Some of the common problems are listed below.
OBD1 connections
The biggest problem with scan tools are older ECUs with the OBD1 connection. Back in the the early 80s when they first started to come out manufacturers made different shaped DLCS for their ECUS. This became a major problem for scan tool creators as they had to create various adapter plugs for them to fit. Some cars also required additional hardware to work which made checking a wide range of cars difficult.
Solution
In the early-mid 1990s OBD1 was replaced with OBD2. Unlike OBD1 which changed from manufacturer to manufacturer OBD2 DLC connections are the same in every vehicle equipped with one, and doesn't require additional connector plugs. This makes it easier for mechanics to diagnose a larger range of vehicles.
In the early-mid 1990s OBD1 was replaced with OBD2. Unlike OBD1 which changed from manufacturer to manufacturer OBD2 DLC connections are the same in every vehicle equipped with one, and doesn't require additional connector plugs. This makes it easier for mechanics to diagnose a larger range of vehicles.
Cost of scan tools and lack of additional software
When they first came out they were incredibly expensive. Not only that they were very primitive. Many were unable to acquire new software. This made them very unreliable as you wouldn't be able to use them on later model vehicles later down the track. Some were restricted to only operate on certain manufactures (like ford and GM). This made them extremely annoying as would need a different scan tool for different manufactured vehicles.
Solution
The computer age has made electronic devices more affordable due to cheaper mass production and heavy global competition. Because of this scan tools have become cheaper to mass produce and sell. The software and hardware have also been updated tremendously. Not only are the capable of reading fault codes they can also display live data stream (inputs and outputs) have bi-directional controls (the ability to make the controllers do things outside of normal operations) and may even be able to calibrate/program modules within certain parameters. Though they still vary allot the amount of things they can do usually reflect their price range.
The new IPHONE scan tool application is a major breakthrough as its convenient, compact and very affordable. This has become very exciting as the software and the wireless connector together cost only $130.00 while most automobile scan tools cost around $1500-$8000 dollars. Not only that you can use it to clear the fault codes on a vehicle after repairs. You can also update the software via internet so you have the latest information for modern cars. You can also have someone record data while your driving. Most scan tools are also incredibly big which makes using them a hassle at times.
This video shows an iPhone scan tool being used on a vehicle.
Flash codes
Flash codes were created for vehicles before scan tools became available. Although not seen on many vehicles today many manufacturers still stand by them as you may not have a scan tool nearby to check your vehicle fault codes. As long as you have your car manual (you should have one in your car, honest) and a jumper wire to put between the pins you can read the flash code on your dash. This would let you know what was wrong with your car, or at the very least were to look. This would start by the engine check light popping on when you turned on the ignition. If it remained after the engine had started the system diagnostics has found a fault and you have a problem.
Ill be reciting the test we did in class for WS2 flash codes. The engine we did our work on was a Toyota 4A-FE. As car models vary I will simply be recording the things I did to recover my flash codes. This is not a "How to" procedure on how to check for flash codes as it may vary from vehicle model to model.
Checking for flash codes
1)Turn the ignition on. The check engine light will pop on when the ignition switch is turned on and the engine is not running.
2) Start the engine. When the engine starts the engine light should turn off.
3) If the check engine light remains on , the diagnostics system has detected a fault. or abnormality in the system.
Diagnostic fault codes
1) Turn the ignition switch on.
2) Open the diagnostic plug, use a jumper wire to connect TE1 and E1.
3) Read the fault code.
The faults I got were 24 (intake air temperature sensor) and 41 (Throttle position sensor circuit). I was able to figure this out after I figured out what the fault codes were and checking the fault chart.
After referring to the fault code area I was able to narrow it down to the ares affected. after doing a visual inspection I realized the connections to the IATS and TPS were simply loose. VJ (who made all the faults in each engine) had simply disconnected them then put them back in without snapping them in tight (tricky bastard). Had I simply done a visual inspection without doing the flash codes chances are I would never have known what was wrong with it.
Repairing the faults
It was pretty straight forward as they were simply loose connections, all I had to do was plug them back in. If this was a customers car brought into a work shop it could be a number of things from broken wires, corroded terminals to even a faulty sensor.
Clearing the codes
After repairing the fault (two loose plugs) I took out the jumper wire and turned the car off. I then had to isolate the battery (take one of the battery terminals off) from the ECU and leave it for over 30 seconds. Turned the ignition on and the codes were gone.
How could the faults affect engine performance
As it was a fault with the TPS and the and the IATS the ECU would be getting all kinds of error codes. As the ECU couldn't figure out the position of the butterfly you would have all kinds of problems like
In some vehicles this could lead to your ECU resorting to limp mode. You would need to take your car in to an auto repair shop to get it fixed before you got it back to good running order.
This concludes my Blog. Please let me know if there's anything else you need for this blog and ill get back to you tomorrow.
Flash code scenario
Ill be reciting the test we did in class for WS2 flash codes. The engine we did our work on was a Toyota 4A-FE. As car models vary I will simply be recording the things I did to recover my flash codes. This is not a "How to" procedure on how to check for flash codes as it may vary from vehicle model to model.
Checking for flash codes
1)Turn the ignition on. The check engine light will pop on when the ignition switch is turned on and the engine is not running.
2) Start the engine. When the engine starts the engine light should turn off.
3) If the check engine light remains on , the diagnostics system has detected a fault. or abnormality in the system.
Diagnostic fault codes
1) Turn the ignition switch on.
2) Open the diagnostic plug, use a jumper wire to connect TE1 and E1.
3) Read the fault code.
An example of a flash code
A video on how to check for fault codes on any GM vehicle
The faults I got were 24 (intake air temperature sensor) and 41 (Throttle position sensor circuit). I was able to figure this out after I figured out what the fault codes were and checking the fault chart.
After referring to the fault code area I was able to narrow it down to the ares affected. after doing a visual inspection I realized the connections to the IATS and TPS were simply loose. VJ (who made all the faults in each engine) had simply disconnected them then put them back in without snapping them in tight (tricky bastard). Had I simply done a visual inspection without doing the flash codes chances are I would never have known what was wrong with it.
Repairing the faults
It was pretty straight forward as they were simply loose connections, all I had to do was plug them back in. If this was a customers car brought into a work shop it could be a number of things from broken wires, corroded terminals to even a faulty sensor.
Clearing the codes
After repairing the fault (two loose plugs) I took out the jumper wire and turned the car off. I then had to isolate the battery (take one of the battery terminals off) from the ECU and leave it for over 30 seconds. Turned the ignition on and the codes were gone.
How could the faults affect engine performance
As it was a fault with the TPS and the and the IATS the ECU would be getting all kinds of error codes. As the ECU couldn't figure out the position of the butterfly you would have all kinds of problems like
- Bucking and jerking of the car.
- Idle surging of the car.
- Sudden stalling of the car engine.
- Hesitation while the driver of the car is trying to accelerate.
- Sudden surge in car's speed while driving on the highway.
- Extended crank time when the engine is cold
- Poor fuel economy
- Spark knock
In some vehicles this could lead to your ECU resorting to limp mode. You would need to take your car in to an auto repair shop to get it fixed before you got it back to good running order.
This concludes my Blog. Please let me know if there's anything else you need for this blog and ill get back to you tomorrow.
