Good day eevryone. I have a 98 coupe and recently I noticed that I can no longer sync either one of my two key fobs. I have tried replacing the batteries and when I go through the syncing process, it doesn't recognize either of the fobs. Any idea what is going on? This started about 3 months ago but I don't use the car often at all so didn't really bother me.

 

The VERY FIRST thing that you need to do is figure out if the FOBs work. Take them to a dealer that has a test box or even AUTOZONE has one and make sure that it transmits.

STOP trying to SYNC your FOBs. LEARN THEN and then you can resync them if nessessary... The PROCEDURE is in the owners manual!!!!!

If your 12 VDC battery is weak,, it will cause you to continuously re-sync the fobs (after there re-learned!)

Relearn them and see what happend.

Read and post your DTCs

READING YOUR Engine Diagnostic Codes



The Diagnostic Display Mode is entered with the following procedure:

1) Turn on the ignition but don't start the engine. NOTE! You can read the DTCs with the engine running and or driving down the road but it can distract you. BE careful! Some DTCs clear themselves when you turn the ignition OFF!

2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold OPTIONS
4) While holding OPTIONS, press FUEL four times within a 10-second period.


Initially, on-board diagnostics go into an Automatic Mode which 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. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.
There are two kinds of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current C code indicates a malfunction is present and active 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 English/Metric (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 is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press and hold the RESET button 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.
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. You can GOOGLE the DTC and also find information on it.




Here is very good site that explains the DTCs:


http://www.corvette-web-central.com/C5DTCcode.html


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



Make sure to include the H or C suffix!!



BC

 

I have tried to learn both fobs with no luck as well. I will take them to an autozone to see if they transmit. If nothing else, I will check codes. Thank you.

 

I haven't had a chance to take the fobs to get checked out but here is what I have so far. One thing I notice is that when I go through the process of leaning the key fob, I get to the point where it states "FOB TRAINING" but I read on an article that you must press the reset button to get a message stating "HOLD LK + UNLK 1ST FOB". I never get that no matter how many times I hit reset.

I pulled the following codes. I took a look at them and they all seem historical but I figured I would post to see what you guys thought:

Radio - NO Comm
99-HVAC B0367 H
AO-LDCM B2252 H
AO-LDCM B2282 H
AO-LDCM B2284 H
AO-LDCM U1255 H
AO-LDCM U1064 H
AO-LDCM U1016 H
AO-LDCM U1096 H
A1-RDCM B2253 H
A1-RDCM B2283 H
A1-RDCM B2285 H
A1-RDCM U1064 H
A1-RDCM U1096 H
A6-SCM B0851 H
A6-SCM U1064 H
A6-SCM U1016 H
BO-RFA No Comm

 

The RFA No Comm is the main issue with the fobs. You seem to have some low battery indications so use a meter and check the static battery voltage with the ignition off

 

Are you referring to the main battery in the engine compartment (I have an Optima Red Top)?

 

YES... Have that battery TESTED!! Ive see NUMERUS OPTIMAS **** the bed. Mine died with in weeks of installing it.

MEASURE the battery voltage at the battery terminals during cranking and report the lowest value.

BC

 

Will do.

 

Ok guys. Finally got some measures of the battery.

1) off position with no key in - 12.3v
2) key in on position - 12.0v
3) starting the engine - measures between 10.9v and 13.2v
4) car started - 14.6v

Now I have a full sound system in the car and a high output alternator. Do you guys still think this issue is the battery? I replaced this one with a failed red top about 9 months ago.

 

Battery doesnt seem that bad. As far as I can tell, it shouldnt cause the issue. Know anybody that you can borrow a known working FOB from??

BC

 

No I don't but both fobs were working just fine the last time I used the car. I highly doubt its the fobs given the fact that the learning process doesn't go through all the steps. Anyone else have any idea on this?

 

Well,, I HATE not being there and NOT being able to see and test things for myself. And I hate blaming issues on random things but try this:

If you cant do a FOB relearn session, something is interfering with it. The only thing that I can fault that may be causing the issue, is either a serial data buss issue or a voltage issue. With out having access to a tech 2, the next thing that you can do is clean your ignition switch. If one of the module 12 VDC ( Hot in RUN & START ) voltage is not correct, that could be the issue. It sure will not hurt anything to service it:

- C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html

THOUGHTS????

BC

 

That is a good starting point. What did you use to polish the contacts and how did you polish them since they are so small? Any details on the removal process of the switch as I don't think I saw that on your write up?

 

I used a pencil and cut the eraser so that it easily fit in the contact area. Just Glue the paper on the eraser with some contact cement.
I used 800 wet and dry to get the really bad stuff and pits removed and polished them with 1000, grit. I found that if you assemble the switch with all of the contacts CLOSED, use a paper clip and open the contacts up enough to get the paper in between the contacts, slip the sand paper between the contacts and pull the paper out, (do this a BUNCH of times) it will make the contacts have a much larger contact area (you lap them in so to speak) and the switch will better handle the current load of the circuits better.

2000 grit wet and dry should work for the finial polish. Start with 1000, 1500 and work up to 2000. Do some 2000 grit if you really wanted a smooth surface.

Your working in a small area so be creative!

DO NOT use any grease in the switch contacts!

When your all done clean the contacts with alcohol and MEASURE THE RESISTANCE of each contact before you reassemble the switch to make sure you’re as close to ZERO ohms as possible on each contact.

BC

 

I agree fully with DGRANT. Your key issue here is that the RFA (remote function actuator) that listens to your TPMS and Key Fob transmitters is not talking on the serial OBD-II bus. The Radio "NO COMM" is because you probably have an aftermarket stereo that doesn't plug into the OBD-II bus.

Your TPMS is probably complaining as well, correct? "Service TPMS System", and "XXX" for all 4 wheel air pressures every time you start up.

You need to verify this RFA unit's 3-wire 8-position connector is attached properly to the unit. The RFA is tucked up over the driver-side rear wheel well. The pre-01 RFAs are about 12" long, mostly antenna. You might re-seat the cable and see if it starts responding. If not, a number of folks upgrade their pre-01 RFAs to 01+ to use the cheaper TPMS sensors, so you can likely pick one up in the for-sale section cheap, or from highly-recommended forum sponsors like Marc from VetteNuts.net. Plug'n play, just train your fobs & TPMS.


Cleaning the contacts is always a great idea (I did mine last year following your guide Bill). But the RFA gets unswitched battery power, as it needs to listen for key fobs with no key present.

Todd

 

Interesting. Any idea what I need to remove to access the RFA? Can I access it through the rear hatch area?

I haven't had TPMS sensors on my wheels in a very long time so I have been getting the TPMS DIC messages for a while.

 

I didn't have to remove any panels or covers for '02 tiny RFA, it was just clipped-in under the body panel behind the driver's rear speaker on my 'vert.

The other body styles are supposed to have it in the same place, directly over the driver's wheel slightly toward the front. It's up there (or should be), along with the 8-position connector. If you just find the connector, you may have also found your problem.

Pics at this thread

Todd

 

I'll take a look when I get home tonight. Thanks for the heads up.

 

 

I took a look and it seems like you need to pull some stuff off to access. I can see Bill's picture but how do I get to it? Not sure what needs removed to get to it and how. If anyone can help that would be great!