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chevy02tb
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Jan 19, 2015, 6:43 PM
Post #1 of 22
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no crank no start
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2002 chevy trailblazer LTZ 4.2 143,000 miles.
This is what happen when to start SUV in the morning and it started then died within seconds. Tried 4 times and then there was nothing. This is what I none so far. Replaced starter, starter relay (no change but old one back in),Ignition switch (no change put old one back in.) , battery neg and pos cables. Had battery test and was told it's good. Starter will crank engine with remote starter switch. Test starter relay socket can crank engine jumper 87 and 30. test relay with 9 volt battery on 85 and 86 relay clicks.tested with multi-meter all reading 12.21 neg post to starter, post to post, pos post to alt, pos to engine block, key to crank tested neg to pos post 12.07 check all fuses front and back of vehicle.
Have No scan code in obd2. tried starting in different gears P N D R , Have backup lights in reverse. someone said neutral safety switch where is it located? Can it be tested.
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Discretesignals
Ultimate Carjunky
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Jan 19, 2015, 7:10 PM
Post #2 of 22
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Re: no crank no start
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Test starter relay socket can crank engine jumper 87 and 30. test relay with 9 volt battery on 85 and 86 relay clicks.tested with multi-meter all reading 12.21 neg post to starter, post to post, pos post to alt, pos to engine block, key to crank tested neg to pos post 12.07 check all fuses front and back of vehicle.
If you can jumper 87 to 30 in the socket and the engine cranks, that means your battery, battery cables, and starter is good.
You should not be seeing 12 volts on 85 with your meter connected to battery negative. 85 is the control circuit to the relay. The engine computer grounds that circuit to energize the relay's coil.
When you check your relay, you have to not only check to see if it can energize with your 9 volt battery, but also be able to carry current on the contact side of the relay.
Does the relay click when you turn turn the key to start?
Does this vehicle have an aftermarket alarm system that disables the starter circuit?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jan 19, 2015, 7:11 PM)
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Hammer Time
Ultimate Carjunky
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Jan 19, 2015, 7:28 PM
Post #3 of 22
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Re: no crank no start
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You don't have a security light on or flashing when you try to start it, do you?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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chevy02tb
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Jan 31, 2015, 3:20 PM
Post #5 of 22
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Re: no crank no start
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relay does not click when turning key.
I hook relay 30 to pos. and 87 to neg. on battery ,then using a volt meter took black lead to 85 and red lead to 86 i got a reading of 72.1 on setting 200 ohms.
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chevy02tb
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Jan 31, 2015, 3:22 PM
Post #6 of 22
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Re: no crank no start
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no security light on
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Sidom
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Jan 31, 2015, 5:24 PM
Post #7 of 22
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Re: no crank no start
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I would be curious to see the answer to DS's question about the AM alarm...
If the starter cranks when you jump 12v to #87 then the problem is probably on the control side....
Maybe one of these guys can post a wiring diagram for you.....Start at the ign sw and see where you are losing your power..
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chevy02tb
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Jan 31, 2015, 5:33 PM
Post #8 of 22
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Re: no crank no start
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have wiring diagrams but do not understand the testing part.
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Sidom
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Jan 31, 2015, 5:57 PM
Post #9 of 22
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Re: no crank no start
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This one is pretty basic........Just look at your diagram.......There is a wire coming out of the ign sw.....I believe its yellow (double check your diagram to be sure, I am at home and am not looking at one right now). This is the power wire for the starter. when you turn the key to the start position, it should have 12v. If not you have a bad sw,or something going on with the key........This is also the wire the an AM alarm will tap into to disable the starter........Look at this wire under the dash an make sure someone didn't cut it in 2 and install an alarm....
So find that wire, get your volt meter and see if you have power on that wire when you turn the key to the start position.......
I believe there is also a fuse for the control side of the relay you may want to check.....so there is 2 fuses that need checking......once again.....check your manual or maybe someone will post up a diagram for you
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chevy02tb
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Jan 31, 2015, 5:59 PM
Post #10 of 22
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Re: no crank no start
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Does this vehicle have an aftermarket alarm system that disables the starter circuit? no aftermarket alarm.
30 and 87 on relay jumper to battery and 85 and 86 coil side with volt meter on 200 ohms reads 72.1
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chevy02tb
User
Jan 31, 2015, 6:40 PM
Post #11 of 22
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Re: no crank no start
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okay here is the test for ignition switch.
test light comes on
1 brown first click run, and start.
2 red/white key off,first click run,start and crank and hold forward
3 pink start and crank and hold forward
4 yellow crank and hold forward
5 white first click run ,start ,crank and hold forward
6 red key off first click run ,start, crank and hold forward.
7 orange start
fuse 17 crank fuse ,power light on with key in crank
fuse 22 ign E power light on with key in start. If you blow this fuse you have no dash lights (i know because i did it)
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Sidom
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Jan 31, 2015, 6:48 PM
Post #12 of 22
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Re: no crank no start
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Well....I might not be explaining this correctly.......
It sounds like you took a jumper and jumped between #30 & 87 of the starter relay and the engine cranked over??? if this is true the you don't need to look at the load side of the circuit anymore.....that side is working.......The problem will lie in the control side......numbers 85 & 86......This side starts at the ign switch and ends at the little terminal of the starter solenoid.......You can check both terminals where the relay plugs into.....One of them should have 12v on it with the key in the run/start positions......We already know that #30 has 12v on it and the fuse is good or the starter wouldn't have cranked when u jumped it.....
If terminal 85 or 86 has 12v on it with the key on then you HAVE to start at the ign switch wire and start tracing it down with your volt meter and see where the power stops......
I don't know how else to explain it.....
I will add this.......Unless you have owned this vehicle since it was new and are positive....I would double and triple check that there is no AM alarm installed......I can't tell you how many no crank no starts I've checked out where the customer swore there was no AM alarm on the car only to find out the reason for the no crank was a faulty AM alarm......
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Sidom
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Jan 31, 2015, 6:58 PM
Post #13 of 22
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Re: no crank no start
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Ok.....not sure where you got that but......#4 is wire I'm talking about and you need to check both of the those fuses that are in your post......
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Hammer Time
Ultimate Carjunky
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Jan 31, 2015, 7:14 PM
Post #14 of 22
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Re: no crank no start
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Here's the diagrram. Don't forget about the neutral switch. That supplied trigger power to the relay and the PCM supplied trigger ground.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
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Jan 31, 2015, 7:37 PM
Post #15 of 22
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Re: no crank no start
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Yep, computer controlled starting. PCM gets a start signal from the ignition switch and a neutral signal when the transmission is in park or neutral. If PCM sees what it likes, it will ground the coil side of the relay to allow high current to flow to the starter motor solenoid when the relay latches. PCM monitors cranking speed and releases the ground when the engine speed goes above cranking speed....hopefully...lol
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jan 31, 2015, 7:40 PM)
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Sidom
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Jan 31, 2015, 7:40 PM
Post #16 of 22
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Re: no crank no start
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Yea.....I'm thinking there is more than just a cranking problem going on here as well
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Discretesignals
Ultimate Carjunky
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Jan 31, 2015, 7:49 PM
Post #17 of 22
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Re: no crank no start
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Screw the ohm meter. You want to test this circuit live. Ohm meters are good for certain tests, but this isn't one of them.
If you don't see battery voltage on fuse 17( on both sides of fuse) with key in crank, head up to the ignition switch and make check there. If you have power at fuse 17 with the ignition switch in the start position, you really need to get hold of a scan tool and look to see what the transmission gear selection is in the data stream and make sure the 12 volts is reaching the PCM connector.
You should also see if 12 volts is sensed by the PCM for the neutral input (dark green wire) with the key on and in start positions. That 12 volts from the neutral safety switch also goes to pin 86 in the relay cavity.
If you have ignition switch voltage at PCM and you have 12 volts on the neutral input, and you don't see ground control using a test light at the PCM connector for the relay control circuit when you turn the key to crank, needs a PCM.
So simple to troubleshoot, my granny could do it...hahaha..
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jan 31, 2015, 8:21 PM)
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Hammer Time
Ultimate Carjunky
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Feb 1, 2015, 6:49 AM
Post #19 of 22
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Re: no crank no start
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22 should have power anytime the key is on and 34 should have power all the time. You nered to find out if the green wire coming out of the neutral switch has power with the key on.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Sidom
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Feb 1, 2015, 12:07 PM
Post #20 of 22
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Re: no crank no start
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Ok....lets do this a different way.......I'll keep this short so its not confusing
Take the starter relay out of the box.......get your voltmeter and probe all 4 terminals (the connecters the relay plugs into). Check all of them with the key on and then have someone hold the key in the start position and check all 4....
2 of those terminals need to have 12v on them and the other 2 need to have good grounds......
For power check.....hook the neg (black) lead of the meter to a ground and probe all 4 terminals with the pos (red) lead
For ground check ...hook the pos lead to a 12v power source and probe all 4 terminals with the black lead.......
This may not bet the "best" way to test a circuit (ie not load testing it) but it is the safest way....
I am assuming your are using a digital voltmeter that costs more than $20.......
Back in the day....it you had a digital voltmeter....that meant it was safe for computer circuits........Now adays (thank you China) this is no longer true......
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chevy02tb
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Mar 18, 2015, 4:55 PM
Post #21 of 22
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Re: no crank no start
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problem solved
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Discretesignals
Ultimate Carjunky
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Mar 18, 2015, 5:19 PM
Post #22 of 22
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Re: no crank no start
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Care to share your solution?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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