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 Pete Your Own Question
Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 29096
Experience:  14 years GM dealer Technician.
Type Your Chevy Question Here...
Pete is online now
A new question is answered every 9 seconds

Bought 04 1/2 LLY truck. Sat week, no start, U0105 DTC. Blew

Customer Question

Bought 04 1/2 LLY truck. Sat for 1 week, no start, U0105 DTC. Blew EDU fuse immediately. Sent FICM to be repaired, declared unrepairable (4 layer board burned all the way through by leaking electrolytic capacitor). Checked for harness damage at FICM tiedown point, found and repaired minor damage to one wire, checked for power at FICM connectors pins 3 & 118, OK, checked for grounds at pins 2& 114, OK. Installed 'new' Bosch rebuilt FICM, engine started and ran perfectly for 15 seconds, stalled, DTC U0105. Checked injectors for grounds and shorts:1,2,& 5, 0.5 ohms,3,4,6,7,&8 0.4 ohms. Checked control lines on pins 44,45,47,48,65,64,66,&67 for grounds,OK;also checked CAN lines on 90&91 and engine speed input line on 94 for grounds, none found (used 10 megohm Fluke DVOM). Installed second newly reconditioned Bosch FICM. This one would not start at all, gave DTC U0105.Seems highly unlikely to me that I would have even one bad Bosch unit, let alone two. Sent first reconditioned Bosch FICM to be repaired, was told by repair tech that 'the chip' was bad, he thought by a shorted or grounded injector, even though I didn't see it with my meter. What do you think? Thank you, Hunter***@******.***,***-***-****.
Submitted: 2 years ago.
Category: Chevy
Customer: replied 2 years ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Pete replied 2 years ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

My info is somewhat limited on your model here but I had seen no one else has responded and would like to see if I can help here.If at any time you feel that I cannot help with this please let me know.

From what is described here this sounds like a fault with shorted wiring leading to the FICM.In some cases this short can be on the sides or tops of the valve covers or in the engine wiring harness.I would fully inspect each harness carefully to locate and repair any shorts found.If this is checked and all found to be o.k. let me know so we can continue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete.

Customer: replied 2 years ago.
Checked injector lines for shorts to power, none found. With black/common/ negative lead of the Fluke grounded, injector leads all showed -0.5 to -0.8 volts. I don't understand this but because they all showed this small negative voltage I'm not inclined to worry about it. All checks made at disconnected FICM plugs.
Thank you
Expert:  Pete replied 2 years ago.

Were the injectors tested at all to see if one or more of them have any internal circuit faults that may be causing this issue here?

Customer: replied 2 years ago.
as my original problem statement says, I checked all injectors through the FICM wiring and found resistance to be 0.4 to 0.5 ohm. Thank you Hunter
Expert:  Pete replied 2 years ago.

O.k.,unfortunately I will have to open your question up for others here to see if anyone else can assist further on this due to the difficulty of this issue here.I hope you can get this resolved with ease.

Thanks Pete

Customer: replied 2 years ago.
I have now checked ALL FICM wiring at the FICM connectors for shorts to ground or power, none found. I had previously checked all injector power wiring but had checked the low voltage lines from the ECM only for grounds. I am very close to deciding that Bosch did screw up these two reconditioned FICMs and therefore about ready to gamble the repaired one to see if the truck runs. I await your comments. Thank you, Hunter
Customer: replied 2 years ago.
On Monday I installed a newly repaired FICM in the truck. The U0105 code was there as soon as I turned the key on (but did not crank) . This demonstrates that the problem has to be in the CAN bus system. Can the ECM (the bus master) cause this code? I will learn today or tomorrow whether the FICM is bad.
If I get useful help on this problem I will give good feedback, but the problem is not yet solved. Thank you. Hunter
Customer: replied 2 years ago.
What should be the voltage to each other and to ground of communication circuits 2361 & 2362 on pins 90 &91 at FICM connector with KOEO? Thank you, Hunter