Question about 2004 Pontiac Grand Prix
Car dies and has trouble shifting into overdrive.
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Posted on Jan 02, 2017
some of the trannys has straps in them that sometimes needs to be tightened and that could be the cause of it
Posted on Mar 24, 2009
this trans is the 4T65E. It needs a 4th clutch hub. The splines strip off around 120k or more because they weren't hardened from the factory. The new ones have the hardened splines. The trans needs to come out and be partially torn down. I've fixed alot of these. Change the EPC solenoid while you are there. They wear and hang up causing intermittent harsh shifts
You can drive them forever without changing the hub but you'll never have 4th gear
Posted on Apr 02, 2009
Hello! You're symptoms sound very much like a common problem associated with the fuel pump resistor. The GTP engine has a two speed fuel pump. There are two relays that control the fuel pump via the PCM module. The fuel pump relay and fuel pump hi-speed relay. Tied into the hi-speed relay is a fuel pump resistor that may go bad.
Symptoms vary but primarily the engine will start but die in a matter of seconds due to insufficient fuel pressure.
Here is a picture of the relay - which is located in the fuse box in the engine compartment:
What you can do to both diagnose this and either narrow it down to this or disqualify it as the culprit is remove relay #15, and bend out the tab labeled "85", and then reinstall the relay. If this does solve your problem, then you need to replace the Fuel Pump Resistor. Doing this will bypass the resistor, and place the fuel pump in "high" speed mode at all times. Once you have replaced the resistor, you need to bend the tab back to its normal position and replace the relay.
NOTE: while this may be a helpful diagnosis tool, and provide a temporary fix - doing this procedure for a prolonged period of time can lead to fuel pump failure. Use this at your own risk.
Hope this helps and good luck!
Posted on Sep 25, 2009
DTC P0641 The powertrain control module (PCM) provides a 5-volt reference to the
The throttle position (TP) sensor 1
The accelerator pedal position (APP) sensor 2
The engine cooling fan speed sensor
The AC pressure sensor
The fuel tank pressure (FTP) sensor
The oil pressure sensor (OPS)
The PCM monitors voltage on the 5-volt reference circuit. If the voltage is higher or lower than required, DTC P0641 will set.
Conditions for Setting the DTC
The PCM detects a voltage that is higher or lower than required on the 5-volt reference circuit. The above condition is present for 1 second. Action Taken When the DTC Sets The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. A current DTC, Last Test Failed, clears when the diagnostic runs and passes. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. Clear the MIL and the DTC with a scan tool.
Yes i can be dangerous, depending which issues mentioned above has triggered the code such as a faulty gas peddle position sensor. the code can also cause a reduced engine power to activate.
Thank you for using Fixya and best advice is to have the dealer address these issues. A tech 2 scanner would be needed to address the P0641 DTC code.
Posted on Mar 19, 2010
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