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TIM MOHR
TIM MOHR, ASE MASTER TECH
Category: Chevy
Satisfied Customers: 15121
Experience:  30 YRS EXPERIENCE, FOREIGN AND DOMESTIC, GAS AND DEISEL
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I have a 98 Camaro and it's setting a p0748 dtc pressure

Customer Question

Hi I have a 98 Camaro and it's setting a p0748 dtc for the pressure control solenoid circuit and I'm not what the circuit high or circuit low means is that just another word power and ground? I found the pins for the pcm for the control solenoid but not sure where the problem lies at I changed the internal harness in the transmission and that didn't correct the issue and I'm confident it's in the wire harness between the pcm to the transmission but not sure if it's the high or low the car won't command the up shift during wide open throttle conditions but drives and shifts normal
JA: Sometimes things that you think will be really complicated end up being easy to fix with Chevy. The Chevy Mechanic I'm going to connect you with knows all the tricks and shortcuts. Are you hoping to fix this yourself?
Customer: Yea I'm in the process of hunting it down but just not sure of where to look next and need some insight of some terms high and low
JA: Great! What have you tried so far?
Customer: Changed the harness inside the transmission and changed the solenoid and now trying to trace where the problem is
JA: Is there anything else important you think the Chevy Mechanic should know about your Chevy?
Customer: Well the engine and transmission is built with mild performance parts that's about it not sure if this issue was already there before I built the transmission or not
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Chevy Mechanic about your situation and then connect you two.
Submitted: 6 months ago.
Category: Chevy
Expert:  TIM MOHR replied 6 months ago.

Hi, my name is ***** ***** engine do you have in this?

Customer: replied 6 months ago.
5.7 ls1 with c/h/I upgrades
Customer: replied 6 months ago.
Also 4l60e built with upgrades
Expert:  TIM MOHR replied 6 months ago.

have you reprogrammed the PCM with any type of tuner?

Customer: replied 6 months ago.
The pcm was tuned last year but it was giving me this issue way before the motor build and the tune he changed the line pressure but didn't for recreation the issue on my scan tool I can watch the amps fluctuate between its ref. Amps of .66 and .68 it jumps between that and when I give it throttle it losses power and throws the code at idle it sits between its duty cycle %until acceleration is applied I wanna say when the throttle % gets above I wanna say 60 the amps dropped to about to .30 and everything zeros out and sets the code
Expert:  TIM MOHR replied 6 months ago.

the code you have is for the pressure control solenoid, was it a custom tune, or did he use a specific tuner?

Customer: replied 6 months ago.
He came to my house he is a calibration tech at GM I think he used hp tuner or his own stuff can't remember
Customer: replied 6 months ago.
He used his laptop during the tune
Expert:  TIM MOHR replied 6 months ago.

a tuner is used to checnge the pressure con trol, and can set this code, but you said it was there before he did this?

Customer: replied 6 months ago.
Yea this problem was going on way before the tune and the engine build I just ignored it the transmission was built 4 years ago that's when I really noticed it but really didn't go into depth with it until late I did the engine it drives normally just only under wide open throttle it doesn't command the up shift for no gears
Expert:  TIM MOHR replied 6 months ago.

ok, then you need to ohm out the wires between the transmission connector and the PCM, and see if either of them is open, or shorted to ground, if they are good, then its going to be a bad PCM, have you done this yet?

Customer: replied 6 months ago.
Not yet I used my test light and logic probe on both sides where do I hook the meter too? And what to look for on the readings?
Expert:  TIM MOHR replied 6 months ago.

unpl

Expert:  TIM MOHR replied 6 months ago.

do you know which wires at the pcm to check?

Customer: replied 6 months ago.
Is that tied into the transmission some type of way?
Expert:  TIM MOHR replied 6 months ago.

Yes, the pcm controls the computer

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