P0654 and p0748
05-21-2012, 08:51 AM
#1
Teching In
Thread Starter
iTrader: (7)
Join Date: Feb 2008
Location: Mayville, WI
Posts: 44
Likes: 0
Received 0 Likes
on
0 Posts
P0654 and p0748 I have these 2 codes popping up on a 98 ls1/4l60 conversion. They did not appear after I put the car together first, but after tear down of complete car, paint, and re-assembly, they are present. Using the stock harness, and pcm with emissions deleted.
P0654 and p0748
p0654 is no engine speed signal and the p0748 is a trans code, pressure control solenoid circut. To test the p0748 I can test the trans pin connector for voltage/ohms, but from what I have read so far, the trans line pressure is determined via the pcm by throttle position, engine speed, etc., so do I need to figure out the p0654 first before I dig into the trans code? Engine speed is determined by the crank position sensor by the starter, correct?
Any input and past experiences would be appreciated.
P0654 and p0748
p0654 is no engine speed signal and the p0748 is a trans code, pressure control solenoid circut. To test the p0748 I can test the trans pin connector for voltage/ohms, but from what I have read so far, the trans line pressure is determined via the pcm by throttle position, engine speed, etc., so do I need to figure out the p0654 first before I dig into the trans code? Engine speed is determined by the crank position sensor by the starter, correct?
Any input and past experiences would be appreciated.
05-24-2012, 08:37 PM
#2
Teching In
Thread Starter
iTrader: (7)
Join Date: Feb 2008
Location: Mayville, WI
Posts: 44
Likes: 0
Received 0 Likes
on
0 Posts
Just a little update here. Pulled the harness plug off the trans and checked ohms to the pressure control solenoid, came up with 4.6 ohms, acceptable values for the solenoid are 3 to 7 ohms, checked on pins c and d. So the solenoid is ok. checked pins on the harness, I am getting 7.9 volts on pin c, and d is a ground.
Next step, I got a complete trans harness with all the solenoids connected, plugged the harnes into that. Cleared all codes, then started car, and th p0748 popped up right away. So just like checking the pc solenoid for ohms, this tells me that the problem is from the trans to the ecm.
Checked the wires from the plug to the ecm, they both look good, tested for continuity, both are fine. Whats next? Tomorrow I am going to take the ecm over to West Bend Dyno and have them go into the ecm and see if they can come up with anything thats wrong.
As for the p0654, changed the cam and crank position sensor, but have not started engine to see if anything has changed. Chased the whit wire from the ecm, pin 35 on blue connector, everything looked fine, no fraying or broken wire.
Will update with more as it comes.
Next step, I got a complete trans harness with all the solenoids connected, plugged the harnes into that. Cleared all codes, then started car, and th p0748 popped up right away. So just like checking the pc solenoid for ohms, this tells me that the problem is from the trans to the ecm.
Checked the wires from the plug to the ecm, they both look good, tested for continuity, both are fine. Whats next? Tomorrow I am going to take the ecm over to West Bend Dyno and have them go into the ecm and see if they can come up with anything thats wrong.
As for the p0654, changed the cam and crank position sensor, but have not started engine to see if anything has changed. Chased the whit wire from the ecm, pin 35 on blue connector, everything looked fine, no fraying or broken wire.
Will update with more as it comes.
05-27-2012, 11:20 AM
#3
TECH Apprentice
iTrader: (21)
Join Date: Jul 2004
Location: Sedro Woolley, WA
Posts: 340
Likes: 0
Received 0 Likes
on
0 Posts
I had the p0748, it turned out to be a bad connection at the 20pin at the trans. The dyno guys can log the ohms on the PCS. Thats how I figured out I had it fixed
