How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Mike S. Your Own Question
Mike S.
Mike S., Chevy Mechanic
Category: Chevy
Satisfied Customers: 7153
Experience:  ASE Certified Master Technician
20625509
Type Your Chevy Question Here...
Mike S. is online now
A new question is answered every 9 seconds

I have a 2002 Chevy trailblazer. The vehicle has been giving

Customer Question

I have a 2002 Chevy trailblazer. The vehicle has been giving me quite a bit of problems. First the vehicle will not start with the key when I turn to start everything shuts off. Before this started happening I was having problems with the gauge cluster the four smaller gauges wouldn't work also the radio would come on and off and the Windows wouldn't work. I was still a veto drive the vehicle but I had to jump start it because the battery keeps going dead and also the brake running light stays on and won't turn off. Now the battery is bad and alternator quit working so I just today replaced the alternator battery ignition switch starter relay and the 125 amp maxi fuse. Another problem that just started is the obd2 port will not read for me anymore it powers up the scanner but does not connect.
Submitted: 1 year ago.
Category: Chevy
Expert:  Roy replied 1 year ago.

good evening my name is ***** ***** I will assist

does the car run now????

Customer: replied 1 year ago.
I can get it to start by using a jumper wire to the starter solenoid ports
Customer: replied 1 year ago.
That's how I know that the starter is working properly I just can't get it to start with the ignition
Expert:  Roy replied 1 year ago.

ok, the small purple wire on the solenoid, does it have 12 volts with the key in the start position????

Roy

Expert:  Roy replied 1 year ago.

wiring diagram for you

Expert:  Roy replied 1 year ago.

how are you making out

Customer: replied 1 year ago.
Sorry I didn't mean to say solenoid I meant the starter relay in the fuse panel I jump the two ports with a wire to get it to start.
Expert:  Roy replied 1 year ago.

ok, then tell me the voltage with the key on??? one terminal should have 12 volts. one other one will have voltage for only 2 seconds. you can see in the diagram I sent you.

Roy

Customer: replied 1 year ago.
Only one of the terminals get power and that's the 12 Volts the other three have nothing. I know one is ground and one doesn't get power until the relay connects but I don't know which terminal is which
Expert:  Roy replied 1 year ago.

first, check the ignition e fuse in the diagram. that is the second feed check the diagram for the what I am talking about

Roy

Customer: replied 1 year ago.
The fuse was bad I replaced it and the lights work on the dash but the key still will not start it and it don't look like the gauges are working
Expert:  Roy replied 1 year ago.

does the security light sty on???

Customer: replied 1 year ago.
No
Expert:  Roy replied 1 year ago.

does the relay energize now??? can you feel it click??? did the new fuse blow????

Roy

Customer: replied 1 year ago.
No it doesn't click. No the fuse didn't blow again.
Customer: replied 1 year ago.
Anything else to test?
Expert:  Roy replied 1 year ago.

just got on. be back to you in a little bit

Roy

Customer: replied 1 year ago.
Ok
Expert:  Roy replied 1 year ago.

sorry, just drove 400 miles today home

ok, we have to check and see if there is voltage from the pcm to the control side of the relay. did you check to see if there was voltage for 2 seconds on the control side??

Roy

Customer: replied 1 year ago.
It has 12 volts on the two ports closest to the engine now but neither of them lose power after 2 seconds.
Expert:  Roy replied 1 year ago.

ok,looking at the diagram, I had a senior moment. the second power or control side is grounded by the pcm. when it grounds the control side it will complete the load side which goes to the purple wire at the starter.

just to be sure, did you try another relay?? I doubt it will work if you have constant power. it is going to come down to the pcm has failed by not grounding the control side. that is part of the programming in the pcm.

Roy

Customer: replied 1 year ago.
I bought a brand new relay and have 2 other relays but none of them are working.
Expert:  Roy replied 1 year ago.

I figured that. it needs a pcm.

Roy

Customer: replied 1 year ago.
Will the pcv also cause all the other problems that it has.
Customer: replied 1 year ago.
Will the pcm also cause all the other problems that it has.
Expert:  Roy replied 1 year ago.

yes it will. it can cause all kinds of issues when it fails. that will be the starting point

Roy

please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Customer: replied 1 year ago.
I replaced the ecu and key and it still does not work at all.
Expert:  Roy replied 1 year ago.

did you re check all voltages again???

did you have the new pcm flashed with your vin number???

Roy

Customer: replied 1 year ago.
No I got the pcm and tumblr with key from my friends trailblazer ltz to try it.
Customer: replied 1 year ago.
I have not checked voltage yet I put the phone in and it didn't start still no security light or anything on. Now the battery is dead so I have to let it charge up a little I forgot to disconnect it after putting the pcm in
Customer: replied 1 year ago.
Pcm not phone.
Expert:  Roy replied 1 year ago.

that will not work. those parts from the other vehicle will not allow your car to start. they must be programmed to your vehicle only. when there is a vin mismatch, nothing will work

Roy

Customer: replied 1 year ago.
The ecu from my trailblazer starts his trailblazer.
Expert:  Roy replied 1 year ago.

did you put your tumbler in his truck too???

Roy

Customer: replied 1 year ago.
Expert:  Roy replied 1 year ago.

does the security light come on?? stay on or flash???

Roy

Customer: replied 1 year ago.
No
Customer: replied 1 year ago.
It comes on when you first turn the key but then shuts off
Expert:  Roy replied 1 year ago.

re check your voltages at the relay.

Customer: replied 1 year ago.
Same thing 12 volts on the two inside terminals.
Expert:  Roy replied 1 year ago.

I am going to opt out. I cannot continue here without actually seeing what you are doing. I do not ever use used parts for confirming failures. maybe someone else has better ideas and can help you better.

Roy

Customer: replied 1 year ago.
It's a used part but is from my friends vehicle that he drove over here and has no issues.
Expert:  Mike S. replied 1 year ago.

Ground the yellow/black wire that comes out of that starter relay and goes to the pcm pin 48 of connector 2, then turn the key to start and see if the starter cranks now.

Expert:  Mike S. replied 1 year ago.

Even before that, ch3eck the "crank" fuse #17 in the underhood fuse block.

Customer: replied 1 year ago.
The fuse is good. When I jump the yellow black wire to ground it does turn over in the on position.
Expert:  Mike S. replied 1 year ago.

Ok, it's either a faulty PCM or the voltage from the crank fuse isn't making it all the way to the PCM. Double-check and make sure that the crank fuse has voltage with a voltmeter or 12 volt test light on both sides on the fuse when the key is on start. Then if it does, check again at the PCM purple wire pin 31 connector 2, again key on start. If it does, then I'm afraid you have a faulty PCM most likely.

Customer: replied 1 year ago.
The crank fuse has 12 volts on both sides with the ignition in the on position. Number 31 on c2 is a green wire not purple. There is a purple wire in number 44 on c2 I tested the wire and there is no power with ignition on or in start position.
Expert:  Mike S. replied 1 year ago.

Ok, first of all. The crank fuse should only be hot when the key is on start, not run or on.

Second, I will double-check that wire at the pcm.

Expert:  Mike S. replied 1 year ago.

here is the wiring diagram I have,

It is a purple wire at pin 31 connector 1.

Customer: replied 1 year ago.
Oh I thought you said c2. I will check c1. What is the reason the crank fuse would have power without the inhibition being in start
Customer: replied 1 year ago.
Ignition*
Expert:  Mike S. replied 1 year ago.

As you can see the wiring diagrams are not the same although they were supposed to be. Yes, C1 now.

Expert:  Mike S. replied 1 year ago.

I thought you just made a mistake typing, is the crank fuse hot with the key on just run?

Customer: replied 1 year ago.
The crank fuse is hot in the run position. I just tested the purple wire and it gets 12 volts when then ignition is turned to start.
Expert:  Mike S. replied 1 year ago.

Are you sure? Something isn't right, the crank fuse #17 in the fuse block underhood feeds that purple wire.

Customer: replied 1 year ago.
I just checked again and there's power at the fuse
Expert:  Mike S. replied 1 year ago.

remove the fuse and check again on both sides of the fuse socket.

Customer: replied 1 year ago.
I switched out the ecu with a new one that I ordered online and they vin programmed the ecu for my vehicle but it still is not working. I checked the yellow black wire again and when I have the ignition off the wire is grounded and I get 12 volts I turn ignition on and it's dead. Also when I turned on the ignition I was expecting to have to do the ignition relearn procedure but the security light didn't stay on so I changed out the tumblr and key to one that's not for the vehicle to see if the security light would stay on and it still didn't stay on. I checked all fuses again and all are good. The crank fuse does not get any power.
Expert:  Mike S. replied 1 year ago.

Just 2 posts ago you said, "The crank fuse is hot in the run position.'

Now you say, "The crank fuse does not get any power"

Which is it, one or the other?

Plus, the crank fuse should have power until the key is on START. That's START not run.

Customer: replied 1 year ago.
I thought I sent a message and corrected myself I was testing the wrong fuse. I tested the right fuse at that time and it wasn't getting power at that time either in the start position.
Expert:  Mike S. replied 1 year ago.

So, let me ask again. Does the crank fuse have voltage at both sides of the fuse when the key is on start?

Customer: replied 1 year ago.
No it has no power to either side of the fuse in the start position
Expert:  Mike S. replied 1 year ago.

Then you probably have a bad wire either feeding or leaving the ignition switch, since you say the ignition switch is new. That is assuming the fuse "IGN A" #34 is still ok.

Customer: replied 1 year ago.
Yea ignition a fuse is good. I check all the ignition and pcm fuses again. What wires should I test for the ignition.
Expert:  Mike S. replied 1 year ago.

Red wire going into the ignition switch, which should be hot all the time and the yellow wire leaving the ignition switch, which should be hot when the key is on start.

Customer: replied 1 year ago.
The red going in is hot and the yellow is hot in the start position
Expert:  Mike S. replied 1 year ago.

Then there must be an open or short in the yellow wire between the spot you just checked and the crank fuse, because that yellow wire feeds the crank fuse and you just said, "No it has no power to either side of the fuse in the start position" when I asked, "Does the crank fuse have voltage at both sides of the fuse when the key is on start?"

Customer: replied 1 year ago.
I should be able to jump from that yellow wire to the crank fuse and it should crank from the ignition then. But now that doesn't seem like it would fix the other problems it is having with the gauges not working radio not working sometimes Windows not working and battery draining.
Expert:  Mike S. replied 1 year ago.

It could if it's actually a short circuit. Jumping won't fix the other problems but it should tell you whether or not the starter is going to crank or not. If the other problems are caused by that yellow wire being shorted out even if you do make a temporary jumper, you are still going to have to find and repair the short.

When you do jump, put an inline fuse in the jumper wire. Just incase you touch to the wrong side of that crank fuse.

Anyhow, let me know if jumping it does finally allow the starter to crank or not.

Customer: replied 1 year ago.
I tried to jump the crank fuse it didn't change anything then I test power at the crank fuse again and it gets power in the start position. Still it will not crank over.
Expert:  Mike S. replied 1 year ago.

I give up, these test results keep going back and forth between testing good and then testing bad. I am going to opt out.

Customer: replied 1 year ago.
Well there is obviously a electrical issue on the vehicle and I just don't know where to look I've tested everything that I know to. Can there be any problem from the bcm or anything.