I have a 2002 Chevy trailblazer LS and it won't start. I've replace the alternator, starter, battery and starter relay and nothing. I really need help cause I been stuck in my car for four weeks. Any ideas?
Don't have Automotive logic probeOK, thanks.
Now, please stop replacing parts and start diagnosing the problem. Could it be the ECU? Yes it could, but it could also be a lot of other things that are more likely to cause a no crank situation. Diagnosing the problem can actually save you a great deal of money in the long run.
In order to proceed, you will need a couple of specialized tools. One - an OBDII code reader/scanner, Two - a digital multimeter (DMM), and (this next one is nice to have on hand) an Automotive Logic Probe.
Here is a link to the Logic Probe:
It is just like a test light, but is computer safe and will let you know if power or ground is present rather than just power like with a test light.
So, do you have these tools?
Please respond so we can continue down the diagnostic tree.
Something is draining my battery but the battery is newOK, now using your DMM, check and see what the battery voltage is when the engine is not running and the ignition key is in the OFF position. It should be at least 12.5 VDC. Now have a helper turn the ignition key to the start position and measure the battery voltage. What is it? If it is above 10.5 VDC the battery then the battery is likely good and is adequately charged.
Now, inspect both battery cables and make sure there is no green grunge disease at either end where the insulation meets the battery terminal or the connecting lug. You might want to see if you can lift the insulation slightly to see if you see any of the green grunge corrosion or if the wire is clean and shiny.
Now we get to see how well your battery cables are doing. With the negative lead of your DMM connected to ground, measure the voltage at each battery terminal using the DMM's positive lead. You should see battery voltage at the positive terminal that equals the battery voltage measured between the positive and negative terminals. You should see 0.00 VDC between vehicle ground and the negative battery terminal. If not, then inspect and clean the various connections going to the battery for both cables.
Now measure the voltage between vehicle ground and the positive cable at the junction box where you can connect a positive jumper cable should you need to jump start the vehicle. This voltage should match the battery voltage give or take a few tenths of a volt (say 12.5 VDC vs 12.45 VDC). Now move the positive meter lead to where the battery cable connects to the starter and measure the voltage. Again, this voltage should match the battery voltage give or take a few tenths of a volt.
OK, now take the meter's positive lead and measure the voltage at each end of the negative battery cable. You should see 0.00 VDC.
If any of the voltages are out of line, then the battery cable or cables are likely bad.
More steps coming. I just wanted to let you have something to begin with and let you know I am working the problem.
Good Luck & more soon.
How do I check to see if the starter is good cause I got it from pick n pull?OK, now on the subject of something that is draining your battery of power.
What really needs to be done is to use a DMM that will not turn itself off after 5 minutes of non-use, set up a parallel connection between the battery's battery post/terminal and the battery cable's terminal and then put the DMM in series with the battery and battery cable and then remove the parallel connection. This will serve to protect the HVAC actuators buried in the dash from being commanded to perform a calibration routine when power is restored and the internal nylon gears from breaking when the calibration procedure is commanded.
Now, after you have successfully set the DMM up as well as the parallel connection, disconnect the parallel connection and wait 30 minutes and then see what the current draw is from the battery and then start pulling fuses one by one to see which circuit is pulling the excess current.
OK, now for the battery warning and the rationale:
DO NOT DISCONNECT THE BATTERY - REMOVE THE APPROPRIATE FUSE(S). Why? Because when you reconnect the battery, the HVAC actuators inside of the dash are commanded to run a recalibration procedure which stresses the old brittle plastic gears inside the actuators and the brittle plastic gears break and leaves you unable to control where the air comes out, or control the temperature of the air, etc. Replacing at least one of them literally requires the removal of the entire dash! So, if you ever need to actually disconnect the battery, such as in the case of needing to install a new battery, be sure and use some kind of Keep Memory Alive device to avoid the HVAC actuator recalibration routine.