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Discussion Starter #1
Hello! I have been a long time lurker getting tons of help from this forum but I'm at my wits end with this one and need to be a little more direct. I have been troubleshooting a no start issue on my 2003 GSXR1000. the bike will turn over and crank strong but will not start. I get a C42 when it does not start, though it will occasionally start and run, or crank and give a C25 instead. I have tested the ignition switch with a multimeter and the signal to the main wiring harness is good, with 100 ohm resistance at the plug with the switch on. I have removed the the ignition switch anyway and checked all the wires for shorts and I believe it is fine.

The thing that is really driving me mad, and the reason I don't think it is the ignition switch is that after i get the C42 code, turn the ignition off and unplug the ECU, all the ground pins on the wiring harness are shorted to the positive terminal on the battery. I have unplugged every sensor/harness to see if they are perhaps faulty and they don't appear to be causing the issue. When the harness is shorted like this, the ignition pin to the ECU on the harness shows 0 ohm resistance, which is what is causing the C42 symptom.

I have already replaced the main wiring harness in the bike thinking it was a shorted wire somewhere but that did not solve the issue. Do you guys have any idea what could be causing this?

Thank you for any help you can give!
 

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How is it all grounds are shorted... if they are dead short I'd say computer is fried? How are you measuring short if unplugged.

Sent from my SM-G920V using Tapatalk
 

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Discussion Starter #3
Thanks for the reply! I unplugged the ECU, then measured continuity across the battery positive and the pins marked ground in the service manual. I mostly just used pin 35 for testing the short. It doesn't seem to be drawing enough current to be a dead short across the battery positive and negative? I'm stumped.
 

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Need to volt drop. Plug everything back in. Key it on. Measure voltage across battery. Remember that number. IE 12.6. At the computer back pin ideally. Pierce if necessary. All battery power should be matching all grounds should be 0.


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Discussion Starter #5
Well, bad news but hopefully helpful for troubleshooting. On GunMetals advice, I hooked everything back up to get the voltage on each pin. The battery drained quickly as the headlights were on and I got pretty normal values, 0 for ground and correct positive voltage on the main pin. After I was done, I noticed that I had left the turn signal relay unplugged the whole time. I charged the battery back to 12.94v, plugged that in, removed the headlight fuses so the battery would last, and measured the pins again. I got to pin 52 before I saw smoke from under the tank and turned off power. Ignition Coil #1 definitely no longer works. 😬 These are the values I got:

1) 11.28
2) 11.34
3) 11.04
4) 0.06
5) 0.06
6) 0.06
7) 0.06
8) 0
9) 11.53
10) 11.57
11) 0.23
12) 4.4
13) 2.2
14) 12.9
15) 4.8
16) 4.8
17) 11.7
18) 0.2
19) 3.7
20) X
21) X
22) X
23) X
24) X
25) 0
26) 0.2
27) 0.2
28) X
29) X
30) X
31) X
32) X
33) X
34) 4.9
35) 0.2
36) 0.78
37) 0.86
38) 3.09
39) 8.88
40) 6.03
41) 0.57
42) 0.05
43) 0.77
44) 0.85
45) 3.94
46) 0.56
47) 4.03
48) 5.25
49) X
50) X
51) X
52) X

Xs are pins I could not easily access in the hurry I was in. Could this all be caused by a bad turn signal relay somehow? Bad ECU maybe? I wouldn't think it is the ECU because as I said, even when the harness isn't plugged into the ECU I still get shorts on the ground pins.
 

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I'd replace the ECU and the ignition coil at the same time. Nothing else you can do at this point. I'm an electrician and even with that, its still very hard to determine what terminals should have a resistive path to ground and which shouldn't- unless there is a description in the service manual. I would have thought it was your stop switch or ignition switch, but the blown ignition coil suggests otherwise. A short on your ecu or ignition coil could pull the voltage low enough on those circuits to trigger a fault.
 

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I'm not sure what pin numbers are so it doesn't do me a lot of good. I'll try to sit and see.

As for coil 1 key on. Should see 12v both sides of the coil. Yes? If you have an automotive meter you should have a mS selecting for fuel injectors. Ground side while cranking it should read about 2.5.

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GunMetal81
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