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I need some help

RynosGP

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I need some help. I'm throwing the P0748 Pressure Control Silinoid (SP?) Electrical. I did a search on ClubGP and from what I read it's a sensor in the tranny that tells the PCM what gear I'm in (Correct?). I'm assuming that the code means it's gone bad. Is there any possibility that there could be something else wrong? Or how hard is it to change this thing? Any procedures? Thanks in advance for you help.

Thanks,

Ryan
 

DaytonaPaceCar

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There is also a TSB for this... see my next post down after this...
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DTC P0748 Pressure Control Solenoid Circuit Electrical

Circuit Description
The pressure control (PC) solenoid valve is located in the valve body. The PC solenoid valve controls transmission line pressure based on current flow through its windings. The PCM determines desired line pressure based on throttle position and other inputs. The PCM then varies the duty cycle on the high side of the PC solenoid valve to control current flow to the solenoid. Current is controlled from about 0.02 amps for maximum line pressure to 1.1 amps for minimum line pressure. The PCM monitors the actual current to the solenoid.

If the PCM detects a commanded current draw that differs from the actual current draw by more than a calibrated value, then DTC P0748 sets. DTC P0748 is a type C DTC.

Conditions for Running the DTC
The PC solenoid valve is enabled.
The system voltage is:
Greater than 11 volts at a low temperature of -40°C (-40°F).
Greater than 13 volts at a high temperature of 151°C (304°F).
Conditions for Setting the DTC
DTC P0748 sets when the duty cycle is outside the range of 0.5-95% for 0.2 seconds.

Action Taken When the DTC Sets
The PCM does not illuminate the malfunction indicator lamp (MIL).
The PCM enters PC solenoid valve diagnostic retest mode. The retest mode conducts the following diagnostic routine:
The PCM de-energizes the PC solenoid valve, resulting in maximum line pressure.
After being de-energized for 2 seconds, the PCM commands the PC solenoid valve ON at 0.1 amp for the retest period of 5 seconds.
If no circuit faults are detected during the 5 second retest period, then the PC solenoid valve is returned to normal operation and DTC P0748 diagnostic is passed. If a circuit fault is detected 3 times during normal operation, then the PCM de-energizes the PC solenoid valve for the remainder of that ignition cycle.
If a circuit fault is detected during the 5 second retest period, then the PCM de-energizes the PC solenoid valve for 2 seconds before reentering the retest mode. If a circuit fault is detected 5 times without returning to normal operation, then the PC solenoid valve is de-energized for the remainder of that ignition cycle.
The PCM freezes shift adapts.
The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
The PCM stores DTC P0748 in PCM history.
Conditions for Clearing the DTC
A scan tool can clear the DTC.
The PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission-related diagnostic fault occurring.
The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.
Diagnostic Aids
Inspect the connectors at the controller, the component and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Wiring Systems.
Extended cranking with a low battery could set DTC P0748.
 

DaytonaPaceCar

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Slips, Harsh Upshift or Garage Shifts, Launch Shudders, Flares, Erratic Shifts and Intermittent Concerns, DTC P1811 or P0748 Set (Replace Pressure Control Solenoid Valve Assembly) #00-07-30-002B
Table 1: Line Pressure Specification Table
Slips, Harsh Upshift or Garage Shifts, Launch Shudders, Flares, Erratic Shifts and Intermittent Concerns, DTC P1811 or P0748 Set (Replace Pressure Control Solenoid Valve Assembly)
1997-1999 Buick Riviera

1997-2002 Buick Park Avenue

1998-2002 Buick LeSabre

1999-2002 Buick Regal

2000-2002 Buick Century

2002 Buick Rendezvous

1997-2001 Chevrolet Lumina

1997-2002 Chevrolet Monte Carlo

1999-2002 Chevrolet Venture

2000-2002 Chevrolet Impala

1997- 1999 Oldsmobile Eighty Eight

1997-2002 Oldsmobile Silhouette

1998-2002 Oldsmobile Intrigue

2001-2002 Oldsmobile Aurora (3.5L)

1997-2002 Pontiac Bonneville, Grand Prix

1999-2002 Pontiac Transport/Montana

2001-2002 Pontiac Aztek

with Hydra-Matic 4T65-E (RPOs MN3, MN7, M15, M76)

This bulletin is being revised to add additional models and model years. Please discard Corporate Bulletin Number 00-07-30-002A (Section --Automatic Transmission).

Condition
Some owners of the above vehicles with a Hydra-Matic 4T65-E transaxle may comment on harsh upshifts or harsh garage shifts, soft shifts, shudders on hard acceleration, or shifts erratic. These conditions may appear intermittently or set a DTC P1811 or P0748. During diagnosis, a low or high line pressure (actual versus desired) may be observed.

Cause
The above condition may be due to any one of the following which may affect line pressure output:

Sediment inside the pressure control (PC) solenoid valve, causing the PC solenoid valve to mechanically bind.
Sediment in the valve body, causing the torque signal regulator valve to stick.
Incorrect transaxle oil level.
Correction

Important
Any of the above conditions may be intermittent, therefore, this test should be performed at least three times.


Refer to the Line Pressure Check Procedure in SI, along with the Line Pressure Specification Table below, to determine if actual versus desired pressures are within the values specified. The Scan Tool is only able to control the PC solenoid valve in PARK and NEUTRAL with the vehicle stopped. This protects the clutches from extremely high or low pressures in DRIVE or REVERSE ranges.

Refer to the Line Pressure Specification Table below. The pressures in the table assume a temperature of 70°C. The pressure will vary with a change in temperature.
 

RynosGP

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That's for the info. Looks like I'll have some checking to do this weekend. Hopefully I won't have to replace it.

Thanks,

Ryan
 

gtphale

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have you recently got a dhp pcm? If you have a gtp it might be a gt pcm. You'll have to check the code on the pcm to make sure. For 97's the code is something like 797 for the gtp, and 756 or something for a gt. Forgot the exact numbers,had the same code found out its the wrong pcm though.
 

RynosGP

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have you recently got a dhp pcm? If you have a gtp it might be a gt pcm. You'll have to check the code on the pcm to make sure. For 97's the code is something like 797 for the gtp, and 756 or something for a gt. Forgot the exact numbers,had the same code found out its the wrong pcm though.
How do I check the number. Is it printed on the label?

Thanks,

Ryan
 

RynosGP

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I looked at the label and all it says is

Digital HorsePower
1997 Grand Prix GTP
Version 1.0

Is there another place that would have the code on it?

Thanks,

Ryan
 

gtphale

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hmm should still be a tag on it with the serial number somewhere. If that tag says its a 97gtp it probably is though.
 

RynosGP

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Thanks. I'll look a little closer. It was kinda dark so I might have missed it.
 

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