Is the AC pressure sensor ground always grounded through the PCM. Not switched when ignition is turned on?

 

Question
Does the AC pressure sensor ground always remain grounded?

I see goes to the PCM

where is the PCM grounded?

 

The ground for the AC Pressure is a “Low Reference” or computer ground…it is always grounded…there are a few PCM grounds…the PCM ground goes to the same ground as the negative battery cable at the engine block above the starter.

 

I am having the same issue with the TC error message coming on

No idea what to check??

 

 

Can you start a NEW thread on your issue !!…you are hijacking this thread…your issue is not related to this AC topic right now !!…if not I will delete your post…thanks !!…PLEASE post this in the Tech section..Bill Curlee has not been active on the Forum for quite some time…BTW cleaning your grounds will not fix your parasitic draw…post in Tech and we can offer you some guidance.

 

OK, very good thanks didn’t mean to hijack, we’ll stay with the C5 tech thread

 

Thanks !!...your post will get more visibility there as few people look at the "sticky threads" !!

 

I know this is discussed ad-nauseum; but...... I am experiencing the P0103 MAF high code. I have done the basics: cleaned MAF, checked wiring, checked for vac leaks, etc. My question concerns reading MAF ref voltage to PCM. They talk about the frequency being above 14,500 hz for x amount of time. I back probed the ref wire. At idle I get 4.20 volts, as throttle is pressed gradually it drops steadily (no jumping around) down to about 3.8 volts. I have done a voltage drop on the ground wire from the connector to battery negative and get .027 v drop; negligible. I also checked for voltage drop on ign voltage wire in MAF harness to battery positive and get .031 v drop, again well with in limits. My question is; can the reference voltage test from MAF to PCM be enought? DO I in fact need to watch frequency on the sensor? P.S. All grounds are clean (as indicated by virtually no drop on ground wire of harness.....). No other codes, drive ability is good as well as fuel mileage???

 

Can you start a new thread with your issue ??…you can just copy and paste and we will try to help you…and include in your profile model year, mods, tune, etc…is this a new MAF sensor ??

 

Thanks for the great info.
After cleaning the connector assembly completely, fill the female side full with a NON-CONDUCTIVE grease, assemble and wipe off the excess. Stops further corrosion and keeps the water/moisture out.

 

Just saying hello to old friends of the Corvette C5 community. It’s April 2025 and I am starting on the ground connector cleanings of my 2003 C5. It seems I will probably just do connector replacements since there is a C5 Ground Splice- Pack Service Kit I guess I am going to go ahead and order from Revolution Electronics. Anyone else working on their grounds lately? I know there’s lots of content about my car’s issues and I also have the complete service manuals.
My current DIC messages include:
Shocks Inoperative
Maximum Speed 80mph
Service Ride Control
Service Column Lock
Service Vehicle Soon

Mike from Indy

 

Mike
Three of those messages relate directly to the Real Time Dampening system. What suspension system do you have? F-45 or F-55? The RTD is not happy with something in the system. The RTD DTCs will lead you in the correct direction for repair.
Please read ALL of the DTCs using the built-in code reader using the IPC.and post them here.
Service Column Lock would be the highest priority repair since it can leave you stranded. Do you have the Column Lock Bypass kit installed? If not, I strongly recommend getting the LMC5 and installing it.

NOTE! IF,, you have the early F-45 RTD Suspension (IMHO), I would have it tuned out of the BCM, disable the RTD Computer and swapping in some Bilstein Shocks, a set of ZO6 or F-51 Springs and sway bars. You will see a massive improvement in the cars handling! The F-45 system is built on the BASE C5 -FE-1 Suspension.

BC

 

Hi Bill
Thank you for the great information. I have the Magnetic Selective Ride suspension, which I understand is F-55.
I just completed the complete cleaning of grounds 101 and 102 (with the eyelets) including disassembling/unplugging the connector housings and cleaning all pins and their receiver clips. There was no real visually-noticable corrosion like in the pictures above, so I am not buying the ground splice pack kit yet. I also cleaned the posts and metal contact areas and the other single wire with eyelet that also connects to those two posts. Put it all back together and started the car. Results were:
Start 1: NO DIC messages (whaaa?)
Start 2: All the previous DIC messages except the Service Column Lock (darn!)
Start 3: No DIC messages (really?)
Start 4: No DIC messages (hmmm)
Start 5: No DIC messages (whoa!)
I am not sure what to think of these results and am not confident the problem is solved, I called it a day and will try starting it again tomorrow evening after work.

There's a built-in code reader? I didn't know that, I'll have to google it. I have the BlueDriver Pro Scan Tool. I ran a scan with it several months ago, then put down the Corvette project for a while until now. I am learning how to use it and make sense of the scan results. I'll give it a fresh scan again tomorrow and post the DTCs here.
I don't have the Column Lock Bypass kit installed. I didn't know about the LMC5 kit. I just now ordered it along with the CAGS skip device. I was excited to see that!
Thank you for your help!


Mike

 

TRY THIS!!! You don't need no stinking scanner! LOL

READING YOUR C5 Engine Diagnostic Trouble Codes (DTC)



This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.



The Diagnostic Display Mode is entered with the following procedure:

1) Turn on the ignition but don't start the engine.

2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)

3) Press and hold the OPTIONS button

4) While holding OPTIONS, press FUEL button four times within a 10 -second period.



Initially, the on-board diagnostics will go into an Automatic Mode which will cycle through each module and shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each module. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display. Press OPTIONS again to enter the MANUAL MODE.



There are two types of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes. More likely it's an indication of an intermittent malfunction.



Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.



Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code/s is/are displayed, and if more than one are present; press GAGES to go forward or FUEL to go back through the displayed DTCs..

To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.

NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.



If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.



Once you have the codes, the next question is: What to do with the information?

First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.



NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.

WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.



These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs



Here are some very good sites that explain what DTC mean:



http://www.gearchatter.com/viewtopic11755.php



http://www.obd-codes.com/trouble_cod...d-ii-codes.php



Make sure to include the H or C suffix when you post your DTCs!!



NOTE!!! Start the car and let it idle. Then take it for a drive and see if driving causes the problem to occur. When you return home pull the codes BEFORE you shut off the engine. Remember! Turing the ignition OFF can cause some set DTCs to clear.


Do NOT discount the codes with the H following them. They can provide an audit trail for issues going on with the car. They ARE important in diagnosing problems.

Post ALL the codes that you pull with the engine running..........

Some codes go away WITHOUT setting an H code when you shut the engine off. I suspect you will have several codes that will show C or HC that do NOT show when the engine is turned off.

 

I have the car up on my QuickJack with the rear wheels off. This Sunday the weather is looking pretty nice so I'll finish up what I am doing and take it for a ride then. I am also accessing the ground connectors 201 and 202 to pull them apart and clean them. Getting something on that bolt to unscrew it is my biggest challenge there.
After multiple starts and engine runs (still on the quickjack), I ran the self-diagnostic and got all the DTCs with key ON and engine OFF. I don't know if they are valuable without driving it again but here they are. All are History except B2860.
Its probably best that I clear all of these and see what appears after driving it so I will.
All are History except where noted
10-PCM Powertrain Control Module
P1571
P1652
P1689
28-TCS Traction Control System
C1242
C1277
38-RTD Real-Time Damping
NONE
40-BCM Body Control Module
B0432
B2587
58-SDM Sensing & Diagnostic Module
U1040 Lost comm
60-IPC Instrument Panel Cluster
NONE
80-RADIO
NONE
99-HVAC
NONE
A0-LDCM Left Door Control Module
B2282 battery #1 circuit
B2284 battery #2 circuit
B2262 horizontal position sensor circuit
B2264 vertical position sensor circuit
U1064 comm
A1-RDCM Right Door Control Module
B2283 battery #1 circuit
B2285 battery #2 circuit
U1064 comm
A6-SCM Seat Control Module
B0851 Battery 1 out of range
B0856 Battery 2 out of range
B2605 Seat Front Vertical Position Sensor Failure
B2606 Seat Rear Vertical Position Sensor Failure
B2860 H C Telescoping Column Position Sensor Failure
U1255 comm
B0-RFA Remote Function Actuation
NONE