Thanks anyway.
cruise control expert please
Thread Starter
Le Mans Master
Joined: Jul 2010
Posts: 5,962
Likes: 712
cruise control expert please
1999 c5 6mn. Never had a problem since i bought the car back in 2000.
My cruise can be set at 24mph no problems but now i can't set cruise untill 48mph. It's doubled mph but when it sets at 48mph the display shows 24mph and so on. If i set at 60mph the display shows 30mph. Anyboby have a fix for this. No codes. I have a lot a 25 to 30mph street that are long and cops radar these streets all the time. That's why i need cruise control at 25 to 30mph range but now i can't turn on untill 48mph min????????????
:cra zy:
My cruise can be set at 24mph no problems but now i can't set cruise untill 48mph. It's doubled mph but when it sets at 48mph the display shows 24mph and so on. If i set at 60mph the display shows 30mph. Anyboby have a fix for this. No codes. I have a lot a 25 to 30mph street that are long and cops radar these streets all the time. That's why i need cruise control at 25 to 30mph range but now i can't turn on untill 48mph min????????????
:cra zy:
Last edited by helga203; Jul 22, 2013 at 08:59 AM.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Well.......... The cruise control functions, comes from the TAC Module. I don't know why you would get different set speed.
I'm not sure if the TAC module transmits that cruise speed message and speed or not. But,, its something to think about.
Have you checked for DTCs. I doubt if you will have any cause the system is setting a speed so it doesn't know if its broke or not.
The vehicle speed comes from the VSS and that sensor supplies the PCM with a speed signal. The PCM may also be the cause of the issue
The PCM sends the IPC a VSS signal.
Heres a shot in the dark. Disconnect the battery for a short period of time and reconnect. Clear all DTCs and see if the issue still exist.
BC
I'm not sure if the TAC module transmits that cruise speed message and speed or not. But,, its something to think about.
Have you checked for DTCs. I doubt if you will have any cause the system is setting a speed so it doesn't know if its broke or not.
The vehicle speed comes from the VSS and that sensor supplies the PCM with a speed signal. The PCM may also be the cause of the issue
The PCM sends the IPC a VSS signal.
Heres a shot in the dark. Disconnect the battery for a short period of time and reconnect. Clear all DTCs and see if the issue still exist.
BC
Thread Starter
Le Mans Master
Joined: Jul 2010
Posts: 5,962
Likes: 712
Well.......... The cruise control functions, comes from the TAC Module. I don't know why you would get different set speed.
I'm not sure if the TAC module transmits that cruise speed message and speed or not. But,, its something to think about.
Have you checked for DTCs. I doubt if you will have any cause the system is setting a speed so it doesn't know if its broke or not.
The vehicle speed comes from the VSS and that sensor supplies the PCM with a speed signal. The PCM may also be the cause of the issue
The PCM sends the IPC a VSS signal.
Heres a shot in the dark. Disconnect the battery for a short period of time and reconnect. Clear all DTCs and see if the issue still exist.
BC
I'm not sure if the TAC module transmits that cruise speed message and speed or not. But,, its something to think about.
Have you checked for DTCs. I doubt if you will have any cause the system is setting a speed so it doesn't know if its broke or not.
The vehicle speed comes from the VSS and that sensor supplies the PCM with a speed signal. The PCM may also be the cause of the issue
The PCM sends the IPC a VSS signal.
Heres a shot in the dark. Disconnect the battery for a short period of time and reconnect. Clear all DTCs and see if the issue still exist.
BC
If it matters my vats are turned off cause i have 3 bar SD tune. I had 2 bar with no problems but when i upgraded to 3 bar this is when this happened. I could not get 3bar tune installed without tunring off vats to take 3 bar SD tune.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Look at this picture. I bet the VSS Output Pulses per Mile is set to 2000 in your PCM.
The above was an example Camaro file I opened which does the VSS sensing a little differently but that 4000 pulse per mile should be in the Vette PCM.
Last edited by lionelhutz; Jul 23, 2013 at 12:58 PM.
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Thread Starter
Le Mans Master
Joined: Jul 2010
Posts: 5,962
Likes: 712
Sounds like something the tuner did. The PCM outputs a 4000 pulse per mile signal to the cluster for the speedometer. My guess would be the new tune changed that output to a 2000 pulse per mile signal. The tuner then found the speedo was reading 1/2 speed so an adjustment was made to the internal PCM numbers used to calculate speed from the VSS pulses to get it read correctly again. Unfortunately, the PCM now has an internal speed 2X the real speed and that's what the other computers read over the serial bus.
Look at this picture. I bet the VSS Output Pulses per Mile is set to 2000 in your PCM.
The above was an example Camaro file I opened which does the VSS sensing a little differently but that 4000 pulse per mile should be in the Vette PCM.
Look at this picture. I bet the VSS Output Pulses per Mile is set to 2000 in your PCM.
The above was an example Camaro file I opened which does the VSS sensing a little differently but that 4000 pulse per mile should be in the Vette PCM.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Good to hear it was simple. So, the tuner was you? 
I completely read your post backwards. The internal speed was 1/2 of the speedometer speed so 8000 would be problem not 2000 like I described it.
I completely read your post backwards. The internal speed was 1/2 of the speedometer speed so 8000 would be problem not 2000 like I described it.