Engine/Transmission (1998.5 - 2002) Help with error codes (APPS/speed control)

[AggieJustin]

I noticed the other day on my drive from the airport that my cruise control wasn't working. Whenever I would push the cruise control on/off switch, the cruise control wouldn't come on. When I got home, I checked for codes and found



P0123 - APPS Signal Voltage Too High

P1596 - Speed Control Switch always high

P1597 - Speed Control Switch always low



I didn't have time to do much about it at that time, so I left it as is. A couple of trips later, the cruise started working again. The other night, the cruise wasn't working again. The only thing I could think of was that I had did a WOT run earlier that night. A couple of start cycles later, cruise was working again.



Does anyone know if the presence of any codes might prevent the cruise from working? Or should I be looking at the cruise switch? It is odd though that I have both a "too high" and a "too low" voltage code.



The other thing is that the service manual shows that the P0123 code will cause a MIL light whenever it is set. But I've never had the MIL light come on, but I know it works since I see it light up at each start cycle.



I haven't tried disconnecting the batteries to clear the codes and see if they are reset (haven't had time). Would it be worth a shot to try a APPS recalibration at the same time to address the P0123 code?



Thanks,



JM

 

[01smokinram]

Codes

If you get in Dallas tomorrow between 3 and 5:30 pm give me a call on my cell and we can meet for a minute to find out what trouble you are having.

 

[kaffine krazed]

Check the wires along the firewall by the dipstick tube for the engine oil see if any of them are rubing against the tube. Another area to check is the steering column where the piviot is if it's a tilt wheel.

 

[OO]

I just lost the cruise control on my truck also. Took some guys from work for a quick ride and it never worked after that. I got the exact same codes as you.



p0123

p1596

p1597



The clock spring has been replaced once already. I hope it's not that again. Did you find the problem on your truck?

 

[AggieJustin]

I traced the line in my service manual to the big plug on the firewall on the drivers side of the valve cover. I opened the plug, made sure it was all clean and the wires were tight and haven't had a problem since.



Not sure if that was the prob or not, but it's working now.

 

[OO]

I'll give it a try. Thanks