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Triston
Triston, MASTER ASE CERTIFIED
Category: Chevy
Satisfied Customers: 1608
Experience:  10 YRS. EXP. ASE CERTIFIED SPECIALIZE IN ALL ELECTRICAL AND A/C ALSO AND ENGINE PERFORMANCE
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2008 Chevy Impala LT 3.5L Flex Fuel No crank, no start.

Customer Question

Hello,
2008 Chevy Impala LT 3.5L Flex Fuel
No crank, no start. Basic code scanner reads UO100 code only. IP display reads
Starting Disabled,Service Throttle,Engine Power Reduced. Everything but engine works. Also, fuel pump relay and ECM relay are clicking very rapidly with key in run position. Had battery tested, its fine, cables good, connections good. All fuses in underhood fusebox tested with DMM for continuity and voltage drop, they're all good too.Every " key on" fuse has voltage except the ones involved after the relays, since they wont latch. Swapped relays, nothing. Checked relay sockets, all have battery voltage, where they are supposed to. All grounds good as well. Starting to think ECM or BCM, not sure though? Dont trust any mechanics around where I live. Everyone, including Chevy dealer, are parts changers only. I can change parts until the car finally works too, I just dont have the huge amount of money to go about doing that! If possible, I would like a real mechanic to walk me through trying to diagnose my car knowing I only have a basic scanner, and a nice quality DMM, and the willingness to do what you ask of me. Also, I have a subscription to Mitchell 1 DIY for most wiring diagrams.
Submitted: 11 months ago via Mitchell1DIY.
Category: Chevy
Expert:  Triston replied 11 months ago.

If you have a voltmeter lets do a live phone call so we can test a few things out so we can resolve this faster, but if you prefer to chats that's fine. Thanks

Customer: replied 11 months ago.
Well, as it turns out. It is now getting dark outside and pouring down rain.Would it be okay if we resume this in the morning?
Its supposed to be clear and sunny here tomorrow . I'm not really sure what I was thinking sending my question tonight? I was probably hoping for you to start me with a list of things to go over .
I sure hope I haven't blown my $38 by asking and not being able to work on it tonight. How do we get back in touch tomorrow?
Expert:  Triston replied 11 months ago.

Tomorrow around 2pm central would be ok. No you haven't lost money just log back in and accept the phone call request . Thanks

Customer: replied 11 months ago.
Okay, thanks.
Customer: replied 11 months ago.
Alright, I'm ready if you are. Let's please do the chat . I mean, I've already paid $38 and we haven't even done anything yet. I'd rather not have to spend an additional $27 for the phone call
Customer: replied 11 months ago.
Hello, I'm waiting to chat with you.
Expert:  Triston replied 11 months ago.

If the batteries and grounds all good I believe the problem is a bad body control module and but here are a few things that you can do to try to help isolate the problem. The only way to know for sure if it's a bad body control module onr any other module we will need a big scan tool like a Snapple or a tech2. First see if you can find out which relay is buzzing and let me know. Next use your multimeter clip onto ground and stick the other lead in pin number two and number six and number 14 on the Data link connector and let me know how much voltage you show on each one of these with the key off. Also reply the the resistance across pin 6 and pin 14. When checking pin 2 you at need to select milivolts.

Customer: replied 11 months ago.
I'm sorry if I've offended you Triston. It's just that , I only have 2 hours of daylight left to do any testing. My money is really tight right now, with my hours being cut, and my wife being laid - off. Btw, if you're reading this, I just checked the ground portion of the relay circuit . It seems that the ECM isn't pulling the ECM relay to ground. Also, the fuel pump relay is pulling that to ground , then letting off continuously. I really hope that you'll chat with me and help me out.
Customer: replied 11 months ago.
its the fuel pump relay that is trying to latch. But, if you unplug it it switches to the pcm relay. I tried to check the ground "switch" pull down that comes from the ecm to the ecm relay and pcm relay. The fuel pump relay is pulling to perfect ground , but not staying there, it is flashing like it is switching on and off. The pcm relay ground from the ecm shows infinite resistance. Both tests were with the key on. Okay, went and tested DLC . Pin number 2 does not have a terminal. Pin 6 has 1.272 volts DC, Pin 14 has 1.272 volts DC. The resistance between 6 and 14 is 60.7 ohms.
Customer: replied 11 months ago.
Btw, the DLC tests just now were with the key off.
Expert:  Triston replied 11 months ago.

That's for the info. Sorry but I really need to explain the results by phone its very complex you may have to have a scantool to continue with diagnostics but talking about it would make a lot of sense you readings reveal a serious problem.

Expert:  Triston replied 11 months ago.

I don't want to take your money but in 6 and 14 reveal real issues it should have 2.5 on both or 1.5 and 3.5 on the other. When the key is off please do a call request so I can explain. I hope things get better for your family

Expert:  Triston replied 11 months ago.

Please accept ASAP while I'm logged in I don't think there is a guy other than a designer of electronics better that me. Thanks

Customer: replied 11 months ago.
All I had was $50 in the bank when I paid the first time. I wish I could talk with you!
Expert:  Triston replied 11 months ago.

Sorry but this the best I can do unless you give a positive rating I want even get credit for helping. The best I can tell you is first there has to be a pin 2 usually purple. But on 6 and 14 the readings you have mean every thing is connected properly on your high speed modules but one of them is not working to isolate which on you need to good scantool and try getting communication with all modules find out which is not communicating and when you find the one that's notake sure it have power and ground to that module, it's missing repair that circuit it all test good that module will need to be replaced and programmed by a Gm dealer. Good luck

Customer: replied 11 months ago.
I thought that didnt sound correct either. I had already checked that before. Are you certain it is with the key off? Because I have
2.5 volts DC on either one with the key in the run position. But, you had told me to check it with the key off.