When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Approached my car and the doors would not open, tried with both FOBs with no luck. Replaced batteries in FOBs and same issue. Disconnected negative side of battery and reconnected and after a couple times it finally recognized my key FOB, started car drove around neighborhood and parked back in garage. Checked functions of both FOBs, lock/unlock/hatch release, all good. Came back to car about an hour later and again no response from car in relation to the FOBs. Manually released door and put FOB in glovebox inductor cubby with no luck, I can hear the RCDLR clicking (like it is supposed to, but no response). I cannot start car or even but into accessory mode. Below is the list of things I have tried to troubleshoot the situation.
Fully charged and load tested battery; Battery Voltage is 12.61 when connected to vehicle, OBDII scanner shows 12.41 of the port which tells me the ECM has power.
Have disconnected battery, both terminals, even overnight to reset everything with no luck.
Replaced battery terminals; the factory design is crap so replaced with solid clamp style.
Removed and cleaned all engine compartment grounds; They all ohm ~.7 ohms back to the negative terminal.
Starter connections are good, I can bypass, by jumping the correct pins of the crank relay sockets, and the motor will turn over.
Removed and inspected underhood fuse block (for corrosion and/or loose pins) and checked all fuses, all good.
Removed and inspected BCM (for corrosion and/or loose pins) and checked all fuses, all good.
Inspected RCDLR connections as well, all connectors and pins looked good.
When you connect battery there is a single ding from inside of car. When you press the door actuator you can hear the RCDLR click (searching for a FOB) but doesn’t open. Open the door manually via the override lever, enter the car, shut the door and the start button lights up green (normal). When I press the button with the brake engaged, I hear a series of clicks from the RCDLR (like normal), the ACC relay under the hood also clicks (which I believe is normal) but nothing else happens. If I press the start button down to put into accessory mode, there is a slightly different series of clicks, but again, nothing happens. I have tried with both FOBs in the glove box slot with no luck. I also tested with the FOBs far away from the vehicle and the behavior is the exact same. I DO NOT get the FOB not detected message (whether they are in the car or not), and the dash never lights up. I can manually turn on headlights, adjust the power seats and sound the horn, but nothing else, no door locks, windows, etc.
Can a Tech 2 scan the vehicle for issues without being in accessory mode?
I do not believe it is the RCDLR because I believe it would give me a FOB not detected if that was the issue.
Maybe the BCM went bad…any other troubleshooting I can try? I am driving myself crazy trying to figure this one out. Thanks in advance.
I would try another battery before doing anything else. A bad cell is all it takes. Some other members on this site have found corrosion on the RCDLR connector pins but I have no personal experience with that. If you have a M6 be sure to park it in reverse always. But in summary, my car is now 20 years old and I can say by experience all of my previous 'electrical' issues have been due to the battery. Even batteries that tested 'good' were no so. Hope this helps!
A lot to digest here but if the backup antenna in the glovebox is faulty the car will not start whether the FOB is either good or bad...the RCDLR will still "click" and you will not be able to get the car either in acc'y or run mode...funny thing you should be getting a "no FOB detected" message...if you have a DVOM you can quicky check the back up antenna circuit after removing it...if this is over your head seek out an auto electric shop in your area....BTW, resistance checking a ground is not the best way...the ground must be dynamically load tested and not statically...a ground wire can have half of its copper strands broken and still check good with an ohm meter...will it be able to carry the current of that circuit back to ground ??....probably not and that is what the purpose of the ground is !!...moving this thread to Tech for further assistance.
C5_Diag,
Appreciate the reply, do you have the procedure to check the RCDLR back up antenna circuit after removing it? My undergrad was in electrical engineering technology, I don't use it much anymore and have forgotten most of the theory/equations, but I do remember how to use a multimeter.
No need to memorize Ohms Law….the connector is just 2 wires…orange(signal) and orange/black (low reference) with antenna disconnected connected red lead of DVOM to orange and black to orange/black…DVOM must be in AC VOLTAGE….push the start button…you should see the approximate voltage below…roughly .780 VAC…to remove the antenna open the glovebox and look up and remove the 3-7mm screws and then push down on the latch holding the lanyard to release it…push in on both ends of the glovebox to drop it down and there are 3 hooks that hold it in….I’m sure you can figure it out…if the circuit tests good the antenna may be bad.
BTW, the Tech 2 will not be able to communicate if not in Acc'y or Run mode...for "ignition function" the BCM and RCDLR must be able to communicate with each other...for "starting" it's the BCM, PCM/ECM, and RCDLR...even without scan tool function we can do some quick information bus diagnostics to maybe rule that out.
No need to memorize Ohms Law….the connector is just 2 wires…orange(signal) and orange/black (low reference) with antenna disconnected connected red lead of DVOM to orange and black to orange/black…DVOM must be in AC VOLTAGE….push the start button…you should see the approximate voltage below…roughly .780 VAC…to remove the antenna open the glovebox and look up and remove the 3-7mm screws and then push down on the latch holding the lanyard to release it…push in on both ends of the glovebox to drop it down and there are 3 hooks that hold it in….I’m sure you can figure it out…if the circuit tests good the antenna may be bad.
for "ignition function" the BCM and RCDLR must be able to communicate with each other...for "starting" it's the BCM, PCM/ECM, and RCDLR...even without scan tool function we can do some quick information bus diagnostics to maybe rule that out.
I still remember Ohms law, it was those 18th century French guy's equations, Fourier and Laplace, I can't and don't want to remember. Appreciate the information, will test tonight to hopefully rule this out.
Related to your second reply, I was thinking about this possibly being a can bus issue, interested to hear your thoughts to rule that out. Additionally, remanufactured BCMs from ACDelco are relatively cheap and available so if you have ideas on how to test the BCM as well, I am all ears. Again, I really appreciate the information.
Yes, a no start can be something in the starting circuit or a CAN bus issue...and with a CAN bus issue there are a lot of strange things you'll see inside the car...one can actually short the high speed bus or the low speed serial data bus to power or ground to see what happens to the car...the modules are fault tolerant and they are not damaged doing this... I can't remember all what happens so maybe I'll do it later...let's see how the testing of the RCDLR and the back up antenna work out and then do some CAN bus checks with what we have...just some basic checks with an ohm meter at the DLC...this check is only one of the few checks I do with an ohm meter...
OK, so I shorted Pin 6 (CAN high) to pin 4 (chassis ground) and saw these things...
1) No acc'y mode
2) No dash lights
3) Radio works
4) Door would not unlock
5) RCDLR "clicks"
6) No start and MIL illuminated when starter button pushed
Codes were...
EBCM U2100 ( CAN bus communication) and MIL illuminated
BCM U2100 also and Lost Comm with ECM, TCM, and EBCM
U2100 Class 2 Data Link Malfunction
U0073 Can Bus Communication
OK, so I shorted Pin 6 (CAN high) to pin 4 (chassis ground) and saw these things...
1) No acc'y mode
2) No dash lights
3) Radio works
4) Door would not unlock
5) RCDLR "clicks"
6) No start and MIL illuminated when starter button pushed
Codes were...
EBCM U2100 ( CAN bus communication) and MIL illuminated
BCM U2100 also and Lost Comm with ECM, TCM, and EBCM
U2100 Class 2 Data Link Malfunction
U0073 Can Bus Communication
Interesting, similar symptoms except my radio does not power up and my MIL light does not illuminate as it sits currently. Are you suggesting I attempt to perform the same test on my car to determine if I obtain a similar response, or any change for that matter? You were not able to pull the codes until you ungrounded the CAN high and put into acc mode, correct?
OK, I grounded out pin 2 (serial data bus) to pin 4 and NO radio, no start, no ACCY mode, door would not unlock but would index and then reindex in a second…no dash lights either…RCDLR clicks when attempting to put the ignition in ACCY mode but no ACCY mode…seats, headlights, and horn all work…let me know if you want to look at the information bus first…I use a CAN test box to plug into the DLC so I don’t have to lay on my back underneath the dash…the lights blink if I am checking 2,6, and 14 and there is communication on those buses.
OK, I grounded out pin 2 (serial data bus) to pin 4 and NO radio, no start, no ACCY mode, door would not unlock but would index and then reindex in a second…no dash lights either…RCDLR clicks when attempting to put the ignition in ACCY mode but no ACCY mode…seats, headlights, and horn all work…let me know if you want to look at the information bus first…I use a CAN test box to plug into the DLC so I don’t have to play on my back underneath the dash…the lights blink if I am checking 2,6, and 14 and their is communication on those buses.
My windows are both currently down so I do not know if they are indexing or not but my car seems to be behaving quite similarly, so yes, I think looking at the information bus might be the best bet. Does your ignition start button light up green like mine does after you shut the doors? I can check and see if my serial data bus pin 2 has continuity to ground or not. I'll lay on my back tonight, but just ordered a CAN breakout box that will be here tomorrow.
Yes, my green start button does illuminate…now I used my Launch scan tool and even with the ignition off and manually entering the VIN I was able to communicate with everything but the ECM, TCM, Airbag (SIR), EBCM…I’ve never tried it on this Launch with ignition off so now I know…I will try my other 3 scan tools tomorrow…some modules are not present in the car…if you want to lay on your back with your ohm meter connected to terminals 6 and 14 and your battery DISCONNECTED you should see 60 ohms plus or minus 3 ohms…terminal 2 to terminal 4 (chassis ground) you should read a little over 4 kOhms…terminal 6 to 4 should read around 7.80 KOhms and same for 14…if they are the same the bus is “balanced”…now reconnect the battery and see what you read terminal 6 to 4 and 14 to 4….normally with ignition in ACCY you should see around 2.5 volts…on serial data bus if communication you will see a fluctuating voltage of 0.1 to 0.7 vdc…12 volts is bad as well as ground…I won’t go into the “technicals” of the CAN bus…you may have some knowledge of it…which box did you order ??
My windows are both currently down so I do not know if they are indexing or not but my car seems to be behaving quite similarly, so yes, I think looking at the information bus might be the best bet. Does your ignition start button light up green like mine does after you shut the doors? I can check and see if my serial data bus pin 2 has continuity to ground or not. I'll lay on my back tonight, but just ordered a CAN breakout box that will be here tomorrow.
Pin 2 to 4 battery disconnected you should read around 4K ohms….4000 ohms…anything less than 350 ohms bad.
4.6 ohms on the Class 2…that’s not good !!…possibly a module or maybe even the purple class 2 data wire shorted to ground or the data wire shorted to ground from the splice pack to that module…there are 2 splice packs one being near the BCM / Audio Amplifier pictured which is SP208 and which the RCLDR is on…SP 205 which I’ll see if I have a picture is located above the DLC and not easy to get too…there is a comb which you pop off the splice pack and looks like a comb and ties all the modules on that splice pack together…I normally use my labscope to check and I’m looking for a 0-7 volt square wave…you can pop off the “comb” on SP208 and since we may have a short to ground on possibly a module jumper a wire from pin A (data line) to each of the other pins and see what the resistance is at pin 2 at the DLC…I’ve never taken resistance reading at those splice packs…done many of C5’s…if the bad module is found jump the RCDLR to pin A and see if everything starts working again…those other modules are not needed for the car to start…if no 4 ohms we will have to look at SP205…is the 8th letter of your VIN the letter U ??
Yes sir, 8th digit of VIN is "U" thank you for all the information and the help thus far. I will be able to test this tomorrow afternoon once I am able to get out of the office, will keep you posted.
Yes sir, 8th digit of VIN is "U" thank you for all the information and the help thus far. I will be able to test this tomorrow afternoon once I am able to get out of the office, will keep you posted.
OK, so hopefully the issue will be on SP208…most likely a bad module bringing the bus down…I’ve seen more shorted to power.
OK, so hopefully the issue will be on SP208…most likely a bad module bringing the bus down…I’ve seen more shorted to power.
Ok, I found the grounded circuit, it is pin C of SP208 which goes to the radio, it metered right at 4.6 ohms. I jumped between 2 and 4 and it reads right above 4.8k ohms between 2 and 4 at the DLC. I connected battery and it did not start, but what I did notice is when I pressed the unlock button on the FOB the red LED in the door lights up, but it doesn't unlock the doors. I am about to try to find the grounded wire behind the stereo and see if I can get this up and running again. Maybe it isn't working because the BCM isn't connected on the Class 2 serial bus? I do have an aftermarket stereo with some adapter harnesses that has been installed since 2012 so something may have failed.
2005 Corvette Unresponsive (need help)
