: Trouble Codes and Car Shuddering

Hotrod Deville
02-05-05, 12:23 AM
Okay, I'm hoping someone can help me diagnose what is going on with my caddy. I have a '94 Concours with the 270hp Northstar. I have gotten the following trouble codes:
P023 H :Electronic Spark Timing Signal Probe
P025 C :24x Reference Low Indicator (ignition control module)
P073 H :Intermittent Coolant Sensor Signal
The problem I am having is when going about 42-43mph the Service Engine light comes on and occasionally the car will shudder, not violently just enough to let you know that something is not right. Also when in lower speeds or decelerating the Service Engine light comes on without the shudder. I have all the service records for the car since it was new and the dealer mentioned this problem (misfiring at 40-45mph) all they did was change the plugs and wires, how long do these last on the Northstar, I'm totally at a lost as to what could be happening any help is greatly appreciated. I am also having a problem with the ride control (I know this is common) just wondering if I could do anything about either the SERVICE RIDE CONTROL that flashes or fix it (not likely) here are the trouble codes: S060 C, S061 C, S071 C, S073 H, again any help would be appreciated.

Hotrod Deville
02-05-05, 09:06 AM

Hotrod Deville
02-06-05, 11:31 PM
Any thoughts at all guys?

02-08-05, 08:16 AM
from what i have heard the shudder at 40-45 is the torque converter locking up, try driving it around those speeds with the gear selector in the D spot not in OD or overdrive, that fixed it for me, i only use overdrive, or OD when i am cruising at 55 or so on the highway, not around town since my seville did the same shudder as yours.

02-08-05, 12:55 PM
From the codes indicating a problem with the ignition control circuit and the 24x signal it sounds like something with the ignition module below the coil pack and/or the wiring in the vacinity of the coil pack. I would dissassemble the coil pack and see if there is any obvious corrosion or connector related problems with the coil pack, coil connections or the module itself. Make sure the high voltage secondary ignition wires are routed away from the low voltage wiring to the module and coil pack and segregated as much as possible. If this fails then replacing the ignition module and/or coil pack or swapping with another coil pack if possible might shed some light or fix the problem.

Same with the coolant sensor. An intermittant on the coolant sensor would cause a driveability issue and check engine light. The coolant sensor is on the rear of the right hand cylinder head (rear head on the drivers side on the end of the head as you look at it from over the left fender) Check the coolant sensor connector, wire routing and/or replace the coolant sensor.

when the check engine light is on there is a current code. when the driveablity issue occurs check the codes ASAP while the engine is still running...you can check them driving along. See what code is set the moment the check engine light comes on to see which one is causing the light to flash on and the driveability issue.