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(SOLVED) Weird fuel pressure symptoms
P0089: "The engine control module (ECM) uses commanded fuel pump flow to determine a desired fuel rail pressure (FRP). The actual fuel pressure is monitored using the FRP sensor. If the FRP sensor indicates a pressure more than 20 MPa greater than desired, DTC P0089 will set." If you've seen... -
(SOLVED) Weird fuel pressure symptoms
Any codes? Since your test of the commanded FPR seems to be having an effect on the engine, if you get really stuck I would leave +5/gnd only connected to the Fuel Rail Pressure Sensor. Break the signal wire between the sensor and the ECM and monitor what the sensor is reading while the... -
LB7: Ficm problems???
Not sure it helps but when I was having intermittent errors on the class 2 data bus, I would find my fuel gauge would go to empty. I think I've narrowed the data bus issue down to an aftermarket radio module (chime and steering wheel control replacement), but not 100% sure until I drive for a... -
05 Sierra Transmission Codes
P0735 is a TCM code for "incorrect gear ratio". Some possible causes are slipping clutches, a bad input or output speed sensor, or bad/intermittent wiring to those sensors. The output speed sensor is on the tailshaft of the transfer case. Other causes that have been suggested are transfer...- dndj
- Post #14
- Forum: Mike L's Trans Talk
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Stalling lb7
Thanks for reporting back on the eventual root cause. Good to hear you got it going. (y) -
Gear Selector Indicator Not Showing Up With New NSBU Switch
Thanks for reporting back. Guessing that the ABS codes could have been a result of the broken TCM's inability to pass the vehicle speed sensor data onto the the ECM and ABS modules which use that as input. I don't have any insights as to the general reliability of TCMs of LB7/LLYs.- dndj
- Post #12
- Forum: Mike L's Trans Talk
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Stalling lb7
Are you still getting the "shift range inhibited"? Points to the trans electricals. -
Stalling lb7
Attached. Looks like a power or ground problem. TCM detects power loss from battery supply at ignition off. Check your harnesses, grounding, and TCM connections. -
Is this Normal?
I'll toss out a theory. It could be the speed limiter. LB7 stock is 98mph I think. At 60mph, with 33" tires, you're getting 10.5 tire rotations per second, or about 1 tire revolution in 1/10 of a second. Under acceleration, a sharp bump could cause the tire pop off the pavement for a half... -
NSBU help
Since you said the 7 pin and 4 pin NSBU connectors were new Rockauto items, perhaps the 4 pin is also bad, leading to your codes? For sure fix the pass through connector seal first. Thanks for reporting back, this may help others in the future.- dndj
- Post #35
- Forum: Mike L's Trans Talk
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My new toy uses Spark plugs !!!!!!!!!!!!
It's Mr. Big's caddy from Smokey and the Bandit! Close at least. Mr. Big had a '74. :)- dndj
- Post #7
- Forum: Things that use Spark Plugs
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NSBU help
Yup. The light should come on in P and N positions only, between C2-E and C2-G. A word of warning: that light bulb could be drawing significantly higher current than what the wiper contacts inside the NSBU are rated for. Normally current passes through these for a relay coil which is...- dndj
- Post #32
- Forum: Mike L's Trans Talk
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NSBU help
Yes. Could cause the clocking of the switch to be off. My GM service manual documents a cable adjustment procedure, but i found this writeup elsewhere on the web, which is pretty much what the manual says. The shift cable comes in two pieces and where they meet there's a slack adjuster. It's...- dndj
- Post #31
- Forum: Mike L's Trans Talk
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NSBU help
Trying to help out and follow here. In post #2 you stated you had +12V power on both pink wires of the NSBU, which would be C2-E and C2-C. Now you're saying there's no longer power on C2-E? Please clarify.- dndj
- Post #26
- Forum: Mike L's Trans Talk
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NSBU help
Cool article here - if you wanted to look inside the NSBU switch and see how it works. It's just wipers running against metal, and it's very clear why both trans and NSBU need to be in neutral before installing. https://gearsmagazine.com/magazine/being-neutral-the-allison-nsbu-switch/- dndj
- Post #22
- Forum: Mike L's Trans Talk
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NSBU help
Next recommendation: put the truck in neutral. Pull the NSBU connectors C1, C2 off. Probe on the NSBU pins and verify C2-E and C2-G are shorted together (they should be connected in P and in N).- dndj
- Post #20
- Forum: Mike L's Trans Talk
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NSBU help
Yes - bulb to +12v on the battery, ground on C2-D of the harness while both C2 and C1 remain unplugged from NSBU. Mechanically, I mean the NSBU is not rotating to the correct position when in Park somehow, when it should be shorting out C2-E and C2-G when in park. Easy to verify - unplug C1...- dndj
- Post #17
- Forum: Mike L's Trans Talk
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NSBU help
After the ground check, from reading your description, another thing that you said in post #2 is a huge clue. When the truck is in P, +12v from C2-E should pass through to C2-G. If you aren't seeing power at C2-G when the truck is in RUN or START position, (and there is power at C2-E, which...- dndj
- Post #15
- Forum: Mike L's Trans Talk
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NSBU help
Don't worry about J1-34 for now. Just verify solid grounding of the NSBU to the battery terminal. Ideally with a load, not just with a digital voltmeter/continuity check.- dndj
- Post #14
- Forum: Mike L's Trans Talk