Jump to content



Photo
- - - - -

Error code p 742


This topic has been archived. This means that you cannot reply to this topic.
4 replies to this topic

#1 97Xcab4x4

97Xcab4x4

    Enthusiast

  • Member
  • 7 posts

Posted 13 February 2007 - 07:41 PM

Can someone tell me exactly what this ( PO 742 ) code means. My tranny has an intermittent problem where the torque converter doesn't want to disengage completely. The truck will leave a stop light in low gear and immediately shift to what feels like overdrive or anything inbetween low and high? . It's like the tranny doesn't know what gear it's supposed to be in. The problem may be around for a day, or two, then go away and not show up again for weeks or months. One thing that seems to cure it is a long drive, if it's acting up, and I drive it for a while out of town, it seems to go away then. It finally sent an error code a couple of weeks ago, my buddy's scan tool came up with the 742 code. What needs to be done to permanently fix this problem? Tranny seems fine anytime other than when it has these intermittent fits. Suggestions please. Thanks


I forgot to add that this truck is a 1997 GMC extended cab with a 5.7.

Edited by 97Xcab4x4, 13 February 2007 - 09:40 PM.


#2 Chanks7

Chanks7

    Enthusiast

  • Member
  • 60 posts
  • Location:St Paul, MN

Posted 13 February 2007 - 11:34 PM

any other codes? p0122 p0123? Sounds like the torque converter clutch is locking up at the wrong time. Check your TP (throttle position) sensor and wiring. The TP sensor is located on top of the engine on the throttle body usually. It has 3 wires going to it, 1 gray 1 black and 1 dark blue.

You can monitor the TP pid with a scan tool or voltmeter. Pull up the TP pid on dataloggin or connect a digital voltmeter from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire).

With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor.

Also slowly fully depress and release throttle and voltage should increase to 5 volts and go vack down steadily without any spikes. If so replace TP sensor.
2003 Z71 Ext Cab LT 5.3
1994 Mustang GT
1993 SVT Supercharged Lightning
Posted Image

#3 97Xcab4x4

97Xcab4x4

    Enthusiast

  • Member
  • 7 posts

Posted 13 February 2007 - 11:49 PM

Haven't had any other codes on the truck since I've owned it. Apparently the previous owner had a EGR issue at one time or another though. Thanks for the info, I guess it's a place to start.

#4 Chanks7

Chanks7

    Enthusiast

  • Member
  • 60 posts
  • Location:St Paul, MN

Posted 14 February 2007 - 12:16 AM

Definitely worth looking at before digging into the tranny.

What kind of egr issue, the egr valve is close to the tp. Was it wiring, they probably share a ground and reference voltage wire.

Edited by Chanks7, 14 February 2007 - 12:18 AM.

2003 Z71 Ext Cab LT 5.3
1994 Mustang GT
1993 SVT Supercharged Lightning
Posted Image

#5 97Xcab4x4

97Xcab4x4

    Enthusiast

  • Member
  • 7 posts

Posted 14 February 2007 - 06:59 AM

I don't know for sure what the egr problem was, I just remember my buddy saying something about it when he was scanning it for the 742 code.




Advertise Here