I left work yesterday (93 Coupe Auto, It's a Ruby) and just as I stop at the end of the parking lot I get a Service ASR Light. I shut it off and restart (WHY?) and it comes back on. I drive 20 miles stop to get gas and when I start it back up no light. Leaving the gas station I feel the need to TEST the ASR System, and it activates. When I get it home I plug in the Tech 1 and get DTC 41 H and Loss of Serial Data. I clear out the codes and drive around the neighborhood for a couple minutes with no more codes.
DTC 41 = RF Valve Solenoid Malfunction.
When I check the FSM it calls for a BREAK OUT BOX, which I do not have, to do any troubleshooting. Any thoughts?

I forgot : I did get a flashing SYS message for just a few minutes, maybe less than a minute and it went away too.

 

sorry to but in. I don't have ASR but my 90 used to get a lot of "loss of serial data" type readings on a scaner. I would unplug each indicated sensor and clean the contact pins with contact cleaner and use di-electric grease on them & put them back together. You might try that on the indicated connection at the indicated part indicated by the code.
JMHO

Tom

 

Thanks for the idea, will do.

 

I cleaned the LF wheel speed sensor, it looked OK, No obvious signs of corrosion. Today on the way to work it did it again, I did not drive it yesterday. I also got the intermittent SYS and SECURITY lights flashing together.
The FSM calls for a J39700 break out box and a BOSCH ABS adapter to troubleshoot, I don't gots!
So I am forced to use logic and common sense here, which I also don't gots. Do the pins in the FSM directly relate to pins in the connector or does the break out box and adapter change them?
Could the EBTCM cause the "Loss of Serial Data" IE: Flashing Sys light? Or could this go back to the ECM/PCM box over the battery(Whichever one I have in a 93 Coupe"? I am thinking if it was the wheel speed sensor I would also get a Service ABS light?
Any thoughts or comments will be appreciated.

 

Anybody have any experience with troubleshooting ASR?

 

I have no direct experience with the Vette system but the code sounds like a problem in the hydraulic unit (that is where the solenoids are located) rather than wheel speed sensor. My son-in-law had the ASR light come on, his was simply a low level in the master. Because the fluid moves when braking, that is when it would light the lamp. He never pulled the code so I have no idea what number it was, presumably something related to level. Good luck, let us know what you find.

 

I've had 'trouble' with my '95 ASR when showing off.
Sometimes the 'service ASR' light would come on after a burn out (I'd forgot to turn the ASR off) and it might go out after the next restart or after the second or third restart.
Eventually stayed out and I didn't worry about it.
Hope this gives you some comfort.
PS look up my other posts regarding ABS, broken wires and bad battery = SES warning.

 

Check your brake fluid level. A little low might cause the code.
93cruiser

 

Thanks for all the help! I checked codes again, this time I think I read it right???? I also checked the brake fluid, it is fine. I just flushed the system a few weeks ago.
CCM 54 Loss of Serial Data
CCM 41 Feds Fuel Cut Off
ABS 72 Loss of Serial Data
It seems that the ECM to CCM connection for the ASR/ABS system is intermittent. I ran all the tests with the Tech 1 and everything worked. The pump that energizes the rear brakes came on for 25 seconds just like it should. After I ran all the tests I drove the car a few miles and no more codes? Do you think that running the system for the test could have solved the problem or do I need to start cleaning connectors?

 

I am far from being an expert on this, but I get a service ASR light whenever my car gets hot. But in mycase, I did the LTCC conversion(LS1 Coils) when I did that, the tach filter needed to be removed in order for the tach to work. I haven't checked any further to see what could be the problem except that a connection that was previously there, isn't anymore.
So maybe check the area of the coil/ign module and tach filter and see if anything is amiss.

 

Thanks, I know I have a busted connector locking device on a module just under the Thermastat housing(Don't know wht it is) I will check on that.

 

The symptoms you describe are very close to what happened on my '92.
The problem for me ended up being the ECM.
When the ECM, under the hood, warmed up from the engine temperature, the ECM would no longer communicate with the CCM over the serial bus.

Replacing the ECM is what solved my problem.

This is not an unusual problem with the '92 and '93 ECM, but does not seem to happen with the later '94 and up ECM.

Tom Piper

 

Thanks for the info! But THAT IS NOT WHAT I WANTED TO HEAR. I have heard that the 93 ECM is getting hard to find? Probably not cheap either?
I don't think my problem is heat related though, it set off the Service ASR light just as I was leaving the parking lot at work, no time to really heat anything up.

 

The reason the '92 and '93 ECM is getting hard to find is because they seem to have a high failure rate.

I checked my system with a Tech-1A too, and I experienced the same problems you are describing.

There are four computers on the same serial link.
They are the CCM (the master computer), the ECM (slave), ASR/ABS (slave), and the C68 climate control (slave, if you have it).

The CCM controls the communications on that serial link.
You can disconnect the cables from the ASR/ABS and C68 climate control units and still run the vehicle.
If the "loss of serial communications" still happens after disconnecting the ASR/ABS and C68, you know that the problem is with the ECM, CCM, or serial link.
In my case, the problem was still there after disconnecting the ASR/ABS and C68 climate control.
But, my problem was definitely heat related, because it never happened with a cold engine -- only after the engine warmed up.

Things to keep in mind:
The ECM and CCM do a security handshake at startup -- if this handshake does not complete successfully, FEDS will shut you down.
If the handshake completes successfully and the communications failure happens after the engine is started, the ECM can run the vehicle standalone even though it is a slave computer.
The CCM receives data from the ECM and passes it on to the ASR/ABS and C68 climate control (by the way, the green LED on my climate control would start blinking too).

Tom Piper

 

Yes, that is what I read in the FSM. The car did not want to start, it took several tries to get it to fire. The FEDS code showed up as a History code.
The CCM is the unit under the dash and the ECM is above the battery?

 

Correct.

The ECM has a high failure rate and the CCM seems to be very reliable.


Tom Piper

 

Where can I get an ECM? Are new ones being manufactured? I am not ready to jump right in yet, the car ran great after I ran all the ASR tests. I want to remove all connectors and try to clean them up before I spend any money. The connectors on the ECM have a locking device I have never seen, what is the procedure for removing them?

 

that may be the problem

I've seen ECM's in Mid America for $99, but you must reuse your PROM.

LIke I said before, I'm far from an expert, but when I did the LTCC conversion, part of the wiring that required me to cut the tach filter off and wire into the ignition module for the tach to work and to turn off the service ASR light. The tach works fine, but the service ASR still comes on intermittently, usually after 4 or 5 runs at the track or on a long road trip. But the way my new ignition works is that the new wiring gets it's signal from the opti to determine crank position and tells the ECM when to pulse the injectors(or something like that). How this is realated to ASR I really don't know except maybe there is a fuel cutoff when ASR kicks in.
When the service ASR light is on, yor ASR will be disabled. That's not usually a problem since most of us turn ASR off anyway. But don't ignore it, still need to find out why, and hopefully prevent anything else from going bad.

 

This is something I need to fix. Like Tom Piper said, the FEDS Fuel Cut off is part of the CCM code 041(I Think it's 41). If the serial link is dead at start up the fuel is cut off. I have read that you can put power to the ALDL to run the Fuel pump, I guess I could do that just to get the car home if it happens again? But I am **** about things and really want everything on the car to work. Right now the only thing that does not work is the drivers outside mirror will not go in & out, only up & down. I tolerate this only because nothing is perfect, so I live with one little problem hoping to avoid bigger ones, like I have now. So much for that theory.

 

In order for ASR to work, it needs rpm, throttle position, and other data about the engine.

Interestingly, the ASR receives the data by different communications links.

The rpm is sensed by the ECM (through the tach filter, or on the '95 and up, the ECM generates the tach signal internally from the Opti-Pulses).
The CCM retrieves the tach signal from the ECM over the serial link and feeds it to the ASR over the serial link.
This is where the "Option Content" programmed into the CCM for your vehicle comes into play. The CCM has to be programmed to know you have ASR before it will attempt to pass the data on to the ASR unit.
That is one reason you shouldn't swap a CCM from another vehicle into yours -- it may not have the same "option content."

However, the throttle position to the ASR is fed from the Throttle Postion Sensor to the TPS buffer (square box beside the windshield washer reservoir), and from there, directly to the ASR unit -- this signal does not go over the common serial link.
The ECM gets the TPS signal directly from the TPS without going through the TPS buffer.

If I remember correctly, the ASR and C68 climate control both receive the vehicle speed signal (VSS) over the serial link -- from the ECM to the CCM to ASR and C68.
That is why the symptoms can provide valuable information for trouble-shooting this problem.
So, if you have:
1) Serial communications failures
2) SYS light flashing
3) ASR light on
4) C68 climate control LED blinking
There is a good chance the serial data isn't there -- that is about the only thing common for all these modules.
And, the '92 and '93 ECM are notorious for having problems.

On another note, it is important to know there are several serial links.
The main serial link is the one for the ECM to CCM mentioned above.
The C68 climate control is on that same ECM to CCM serial link.
In addition, the C68 climate control has a separate serial link to the climate control Programmer under the dash -- so it is on two independent serial links.
And, the radio control head has a serial link the the radio receiver under the dash by the glove box.


Tom Piper