Just after a 1800 trouble free trip in my '96 LT1 during the last 9 days, I decided to perform some service while stopping over at my brother-in-laws before returning home. During this service I disconnected the battery as usual and when I reconnected it, both of the ASR lights came on and would not go out. Also, the idle is now almost 1500 rpm's and the car is almost undriveable due to surging and then almost shutdown.

The brake fluid level is at the full mark and I ran the codes and got H64, H65 and H72 from module 9 and also got "throttle position sensor/switch A circuit low input" on my OBDII code reader from the ALDL. I cannot get the traction control switch to function or clear the ASR codes from the CIS. I do not have my FSM's with me since I am traveling so if someone would be good enough to provide some clues as to what my next steps might be until I can get back home where they are, it would be greatly appreciated.

As a side note, the A/C will not come on now and it has been working great during our trip so I don't know if this is connected to the ASR problem or a separate issue.

Wow... well, first off, welcome aboard.

Sadly, I too am traveling (Sebring for the 12 hours!) and don't have my 96 FSM with me.

Do this... disconnect the battery and put a charger on it. Leave it for 60-90 minutes... then reconnect.

What service did you perform? Are you sure all harnesses are attached for the TPS and such? A loose wire changes all.

Also, a bad tach filter will really screw things up.

I am betting it is connected... The climate controls are integrated into the CCM, so if something is whack there, you have the basis for a real problem.

What service did you perform? Might help narrow things down.

I don't have a 96 fsm, but Brad should, maybe he can chime in later.

Matthew

I serviced the throttle body, MAF and changed the oil and air and oil filter. If someone could help me with the trouble codes I provided it would be very helpful. I understand the first is somehow connected to the TPS but I am not clear how.

As far as the trouble codes:

http://tech.corvettecentral.com/2011/ ... diagnostic-trouble-codes/

"H" represents a history code, and may or may not be current.

64 Bank 2 (Right Front) Heated Oxygen Sensor (HO2S) #1 Circuit (Lean Exhaust Indicated)
65 Bank 2 (Right Front) Heated Oxygen Sensor (HO2S) #t Circuit (Rich Exhaust Indicated)
72 Vehicle Speed Sensor Loss


The O2 sensor problem sounds like a bad sensor or wiring since it is throwing both codes.

The VSS loss I'm not familiar with, but sounds like a wiring issue, as well. The VSS is located on the side of the transmission, driver's side.


You said you serviced the throttle body? What do you mean by that? As in you removed it? Left it on and cleaned it? Most sensors are sensitive to TB cleaner. Did you possibly spray the TPS with cleaner? I would check the TPS voltage with an ohmmeter to see what it registers, closed and open. Also, the ASR is connected to the throttle body, so I'm not sure if there is a reset procedure if the cable has been moved/position changed.

If I give you suggestions on what to check first, I'm just making semi-educated guesses. Without a FSM for a 96 I personally can't tell you the correct troublshooting steps. Someone with a 96 (or 90+) will have to jump in.

Good luck,

Matthew

The MAF was just removed and the air cleaner/intake system was cleaned, not the MAF. I appreciate the reply.

None of these codes appears to relate to the "Service ASR" I have on my CIS that I can't resolve or am I missing something I should not be?

Do you have any codes in mode 4? Double check the connections on the TB. Did you remove the IAC (idle air control) when you cleaned the TB. You might have knocked something loose, which could change the throttle position.

Have you tried disconnecting the ASR?

Check the throttle body to make sure it is closed at idle and not sticking (which was common on older ones).

Did you check the voltage of the TPS?

Matthew

Obviously I am still very mixed up with this process. I see 9.7 on my display and I get the "---" but the CIS display with the ASR messages never clears. On top of that I still have the very high idle. Am I doing this right? I have disconnected the plug to the ASR without any different results.

I have checked and double checked for vacuum leaks and can't find any. The blades appears to be closing almost completely but I don't have an easy way to check the TPS voltage. It is my understanding you can't/shouldn't adjust the TPS but I can't confirm it is getting the correct voltage. Is that 5VDC supply and approximately 0.054VDC at idle?

On my OBDII code reader I am still getting the P0122 error code for the throttle position sensor error. I have changed TPS, IAC and engine computer one at a time without resolving the issue. (I am now back to the original components without any improvement.) My information says the P0122 error code is for low TPS voltage but what might be the cause of this (other than damaged wiring which I have checked)?

I am no expert but might not be considered a novice either. Any suggestions at this point?

The FSM says that it is 5v input from the PCM. At idle the TP sensor should be about 0.6 volts and increase to above 4 volts at WOT. If the PCM senses a signal voltage lower than the normal operating range of the sensor, it will throw a P0122.

They say that it may be a mis-routed harness, rubbed-through wire insulation or a broken wire inside the insulation. It says that vehicles with traction control need to disconnect the EBTCM (Electronic Brake/Traction Control Module) to determine if the short is being caused by it, and to clear any codes that may result from disconnecting the module.

Brad - any way you can take a nice photo of the fsm pages and load it up?

Would you be good enough to point me to the EBTCM (Electronic Brake/Traction Control Module) and tell me the best way too disconnect it? Does it have to be disconnected or does it have it own fuse that can be pulled?

Trying to turn on (or off) the traction control doesn't work since the problems began. Also, could the A/C be connected to this problem? My blower fan runs but I can't turn on the compressor regardless of the panel setting.

Here are the 4 manual pages for the P0122 code:

http://bradprestonmusic.com/Photos/P0122-1.JPG
http://bradprestonmusic.com/Photos/P0122-2.JPG
http://bradprestonmusic.com/Photos/P0122-3.JPG
http://bradprestonmusic.com/Photos/P0122-4.JPG

The EBTCM is in the compartment behind the driver's seat. Here's the info:

http://bradprestonmusic.com/Photos/EBTCM.JPG

It would seem unlikely that a short would've developed in the EBTCM under the circumstances you described, unless something else funky was going on there prior to your other repairs. Seems more likely that something has gone bad in a harness. I don't know about any connection to the AC, though the vacuum check valve on the passenger side of the intake manifold affects both the cruise control and defrost/vent operation.

Pianoguy - Thanks for the scanned information and help. I will check this out first thing tomorrow.

Is there any other check valve in the cruise vacuum hose system, especially where the hose from the dump side of the cruise module goes through the firewall to the brake pedal? There is a larger than normal device on the engine side of the firewall where this hose goes through and I am not clear what that device does. I am trying to chase down everything I can think of at this time and this came to mind. Since a vacuum leak will also cause a higher than normal idle, I want to make certain I have looked at all of the hoses and connections.

Part of what I am going to do tomorrow will be to disconnect every vacuum connection at the intake manifold to see if that might give me some additional leads to solving this problem.

Some good troubleshooting for cruise control:

http://www.vetteweb.com/tech/vemp_100 ... control_repair/index.html

I wish I could help more, but I'm a hands on guy and need to see it in front of me. Plus, I'm not experienced with the newer electronics on the 96 with the asr and whatnot.

Matatk - Thanks for that link. I have seen it long ago but it is excellent information and I will double check my work with it.

I am somewhat of a "hands on guy" myself and am at a real disadvantage without my FSM's right now. This ASR problem is a new one for me and really has me jumping through hoops trying to figure it out. If I can't get this problem solved enough to drive my car back home (which I can't right now) I guess I will break down and take it to a local dealership. This is always a last resort with me but I may not have any other choice right now.

I also have a scanned ABS/ASR manual, but it is hard to use as each page is a jpg - I wish it was in PDF format:

http://bradprestonmusic.com/Photos/96Vette/ABS_ASR-MANUAL.zip

That vacuum hose from the cruise control through the firewall goes to a switch that is mounted on the brake pedal - the switch activates the tail lights and shuts off the cruise.

Have you had a look at the vacuum connection under the TB for the PCV? That hose can get hard and brittle.

Pianoguy - Thanks again for all of your help.

I checked the PCV vacuum connection and it was/is in good shape. Also checked the vacuum hose from the dump side of the cruise control solenoid through the firewall to the brake pedal and have even gone to the trouble to replace the entire section. There was a dounut device on the engine side of the firewall but it doesn't check out as a check valve (maybe something to seal the firewall or hold the hose in place?).

I have also disconnected and plugged each vacuum conection on the intake manifold one at a time chasing vacuum leaks that might cause a high idle without any improvement. It appears the P0122 TPS code is still the problem so I may have to chase down the pin out on the ECM and run some new wires to the TPS sensor. That will be a last resort but might solve this entire problem. Before I do that I am going to try to neatly probe the correct wires looking for 5VDC supply voltage and then the idle voltage of approximately 0.6VDC. If the 5VDC reference voltage is low (which I suspect is the problem) a single new wire might solve everything with code P0122.

Still may have to take the car to the dealer for the ASR problems.

Pianoguy - You may have supplied the key to this problem. Maybe not but I hope so.

On page 13 of your .jpeg's, there is a "TPS module" shown on the passenger side of the engine compartment near the A/C & heater blower motor. Per the information this module contols both the throttle body TPS and the ASR (if I am reading the information correctly).

I haven't located mine yet since it could be a later model car ('96) than your FSM's are for but if my car has this module and it is bad, it could be the solution to this mess.

I will see if I can locate it and let you know. I doubt if this is available anywhere but the dealer but if I can find it, I will call the dealer about one tomorrow morning.

Thanks again for all of the work and scans.

give this a try on your tps . loosen the 2 screws that hold the tps just enough so you can move it up and down since its low you will have to move it up just a little . disconnect the battery while doing this then reconnect and see if the code is still there . if its still low do it again . i would be willing to bet that it solves your problem . if you can find someone with a scan tool you can adjust it using the tool, seeing what it reads out then go up if its low and down if its high . the perfect setting is .54 .you will not hurt the tps by trying this

I saw that too, but my '96 doesn't have anything like that near the blower motor, either - the ABS book is dated 1991 (my FSM's are for the '96 model year, though).

jonszr1 - My TPS sensor has two fixed size mounting holes so once it is installed it cannot be rotated or moved up or down. I have an older TPI 350 Camaro and you can rotate the TPS to ensure you are reading the correct voltages at idle and full throttle but this particular TPS cannot be adjusted. Is everyone's '96 this way or just mine? I have three other LT1 engines and I believe they are all this way.

Thanks for the hint though.

Mine's fixed, too. I was reading about replacing the TPS, and it says:

If the Throttle Position (TP) sensor or the throttle body is replaced, the EBTCM must LEARN the TP sensor idle position voltage with the new component(s) installed. This is necessary to ensure effective engine torque during ASR events. This procedure can be done using the Techline equipment.

1. With the throttle valve in the normal closed idle position, install the TP sensor on the throttle body assembly. Align the TP sensor pickup lever with the tang on the throttle actuator lever.

2. Install the retainers and the two TP sensor screws. Tighten the TP sensor attaching screws to 2.0 Nm (18 lb. in.).

I'm really interested to learn the outcome of this thread since my 94 seems to exhibit almost the same symptoms after an engine rebuild.

I was very impressed by the ABS-ASR booklet copied by Pianoguy, and have converted it into a PDF .. it can be downloaded from ABS-ASR Operation and Diagnosis Manual

It isn't searchable, but it is a little easier to browse!

Tony

Thanks a bunch, Tony!

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Excellent job Tony and Brad!

Flash!!! I am back at home and the car is back to it's super running self. Sorry to be so long posting my short term solution (at least my particular solution to get back home) but my wife didn't want to wait any longer getting to her home. Enough traveling for two or three weeks.

What I ended up doing was going back to the ECM connector and checking for the 5VDC reference and it was OK there. In an effort to get the car running right I pulled off the reference signal there and ran it to the TPS and A/C high side switch. Once I had both with 5VDC, the "service ASR" and "ASR off" went away and the A/C worked. The cruise still isn't working but I really didn't need it to get home. I will work on that in a day or two.

My current plan is to go back and try to trace down the open wire/wires and and repair or replace it completely. It looks like moving everything around while I was cleaning the engine compartment created my problem (possibly helped by the fact the wiring is 15 years old and the car now has 176K on it). If worse comes to worse, I have another complete uncut '96 harness that is in great condition so I will simply replace the entire harness and repair this one when time permits. The extra harness was scheduled to be installed in another project that will not be far enough along to need it for two or three months.

I can't thank everyone enough for all of the great help provided to me. Being away from home and without my FSM's was a real handicap and I don't think I could have gotten the car running well enough to get us back home today without it.

Glad to hear you got a handle on it, Randy!

Glad you were able to get it running! Please post a follow up when you find the specific spot and when you get the cruise working.

Matthew

PS - we love pictures

Quote:

I know where the TPS is, but I'm not sure if I know where the "A/C high side switch" is located ... any guidance (or a photo) would be appreciated. I'd like to try this solution out.

Thanks, Tony

Quote:

Glad to hear it is running, and you know what the issue was.

Here is a pic from a different thread by Bill. In his second photo you can see the high pressure switch, if you look behind the oil filler cap.

http://www.corvette-guru.com/modules/ ... hp?topic_id=14500&forum=1

I tried to use my multimeter and measuring resistances of the wire from each end to locate the open but that turned into a futal exercise so I just cut the gray wires (pins 28 & 29 on the black ECM connector) where the 5VDC references were and ran wires to both the TPS and A/C high side pressure sensor.

Both wires were just crimped so we could get home so I am redoing them by pulling the original pins from the connectors and redoing them correctly. I will have two more wires than the original harness but hopefully no one will be able to see any difference when I am through.

That will probably end this posting so I have started another link with the cruise control troubleshooting. It appears I will need a lot of help with that also, so please bear with me.

http://www.corvette-guru.com/modules/ ... hp?topic_id=14520&forum=1

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Many thanks ... I know just where to look! Tony