Yep... another no-start thread
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Laughing Gas
Joined: Mar 2007
Posts: 898
Likes: 23
From: Tucson
I just felt like I was getting deeper and deeper and when rewording the wirings diagrams, the vref runs from pin 90 through pin 21 of the 42-pin connector right to the CPS. I felt it couldn’t hurt to swap it out with the one I had from Clay.
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,346
Likes: 5,941
From: Lake Hartwell, GA
First time I have seen that issue and resolution. I commend you for your efforts and congratulate you on your victory.
Tell us... Do you do a victory yell when it fired up? I know I would have.
Tell us... Do you do a victory yell when it fired up? I know I would have.
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Laughing Gas
Joined: Mar 2007
Posts: 898
Likes: 23
From: Tucson
Put the hydra chip in, truck ran for about 30 seconds then died. No restart. Pulling the PCM to check the connections. I wiped down the pins with alcohol and let it dry before putting the hydra on and it felt like a solid connection. We’ll see.
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Laughing Gas
Joined: Mar 2007
Posts: 898
Likes: 23
From: Tucson
I did! Until I put the hydra in and won’t start again. Then a loud “wtf”.
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Laughing Gas
Joined: Mar 2007
Posts: 898
Likes: 23
From: Tucson
Thats what I’m thinking. I’m pulling the wiring now and am going to check continuity when I find where the other ends connect. I know one goes to the 42-pin connector. I have a spare pigtail that I’ll put on if continuity checks out. Maybe this one has outlived its usefulness.
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Laughing Gas
Joined: Mar 2007
Posts: 898
Likes: 23
From: Tucson
All 3 go to the 42-pin connector. I have good continuity between the pigtail pins and the 42-pin connector. I have good continuity between the 42-pin and the corresponding pins of the PCM (21, 65, 90). When the 42-pin is connected I get an ohm reading when going from the pigtail to the PCM.
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Senior User
Joined: Oct 2016
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Don't know if this helps but here's a link to riffraff CPS PDF https://www.riffraffdiesel.com/conte...d0QlBvhA-JyShY which has a troubleshooting diagram at the bottom.
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Laughing Gas
Joined: Mar 2007
Posts: 898
Likes: 23
From: Tucson
Plugged in the MX+ to check for codes and it says the scanner is communicating with the phone but not the vehicle with the key on. Checked the ground pins in the OBD II connector and they’re good. Check that I’m getting 12V at pin 16. It’s good. Back to the schematics.
Anyone have a schematic of the OBD II port to PCM? Maybe I have a short somewhere there. There truck started and ran again, then I shut it off and tried to connect the scan tool. Wouldn’t communicate and now back to no start.
Anyone have a schematic of the OBD II port to PCM? Maybe I have a short somewhere there. There truck started and ran again, then I shut it off and tried to connect the scan tool. Wouldn’t communicate and now back to no start.
Logistics Pro
Joined: Oct 2011
Posts: 3,953
Likes: 120
From: Mcdonough, GA
Well congrats on figuring it out the first time.
did you leave the old PCM in the truck. Any chance it's bad and sending higher voltage on the v ref line and frying the CPS? Just spit balling now.
does disconnecting the CPS change anything
did you leave the old PCM in the truck. Any chance it's bad and sending higher voltage on the v ref line and frying the CPS? Just spit balling now.
does disconnecting the CPS change anything
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Laughing Gas
Joined: Mar 2007
Posts: 898
Likes: 23
From: Tucson
Im thinking the plug may have an intermittent connection. I’m working on replacing the plug now, just on a beer break. Hopefully that will fix it but I’m not betting any large sums of money on it.
Will report back when I have the new plug soldered on the reconnected.
As a side note, when I replugged the CPS connector I had the PCM connected outside the truck in the wheel well. Truck fired right up. Disconnected batteries, moved PCM to its normal home, reconnected batteries and no WTS, no fuel pressure. This is definitely a stumper.
If I can get it figured out I’ll drive it home and troubleshoot more; hopefully it makes the 6hour journey.
Logistics Pro
Joined: Oct 2011
Posts: 3,953
Likes: 120
From: Mcdonough, GA
Really seems like a wiring issue near the PCM
