Your check engine light has to be on for autozone to check codes. But you could just tell them its on.
I bought mine from wal-mart for 25 bucks. You plug it in by the brake booster under the hood. There are 2 plugs theres one for the ground and the other one is for the computer. Pretty cool little device you can check you cylinder balance with it also.
Question along the same lines, my check engine light is on, but I am receiving no codes. There are other anomallys that are ocurring (bad idle, hard start, high TPS voltage, fuel pump runs constantly) that may all point to a common thing. Anyone seen any of these problems (the high TPS voltage, 4.25, and constant running fuel pump are my main concern)?
Question along the same lines, my check engine light is on, but I am receiving no codes. There are other anomallys that are ocurring (bad idle, hard start, high TPS voltage, fuel pump runs constantly) that may all point to a common thing. Anyone seen any of these problems (the high TPS voltage, 4.25, and constant running fuel pump are my main concern)?
Grounds are important to any electrical system, and especially to computers.
1.) The main power ground is from engine block to battery: it is the power ground for the starter & alternator.
2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects.
3.) The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery.
4.) All the sensors have a common separate ground. This includes the TPS, ACT, EGE, BAP, & VSS. It is pin 46 on the computer
5.) The O2 sensor heaters have their own ground (HEGO ground) coming from the computer. This is different and separate from the O2 sensor ground.
6.) The TFI module has 2 grounds: one for the foil shield around the wires and another for the module itself.
7.) The computer takes the shield ground for the TFI module and runs it from pin 20 to the chassis near the computer.
8.) The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally.
If you have access to a digital voltmeter and would like help diagnosing grounds, make another post and I will try to help.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)
Thanks for the info, after reading your post I am going to spend some time with it tonight. I do have a digital multimeter so if you don't mind providing additional assistance, I would be most appreciative.
Thanks for the info, after reading your post I am going to spend some time with it tonight. I do have a digital multimeter so if you don't mind providing additional assistance, I would be most appreciative.
The basic premise is to measure the voltage drop accross a connection by placing the DVM test lead on the wire and the other on the other side of the wire or connection. Measuring the drop across the wire or connection shows how good the connection is: you should have less than .5 volts drop.
To find high resistance connections, and excessive voltage drops, put one voltmeter lead on the negative battery post and one on the engine block. Then try to start the car: more that .5 volt drop indicates a dirty connection or bad cable: next try from negative battery post to body ground at the firewall.