OT: problem with 2001 chevro-lett impala and starting in park.

[ryan roopnarine]

ok, i'm kind of at the edge of my ability to investigate this problem.

the car is a 2001 chevrolet impala 3.4l. occasionally, it will not start in park. as it is my mother's car, i gave her a notecard with very explicit instructions about how to start the vehicle in neutral, which, up to very recently, has "fixed" the problem. the last time this occured, however, shifting to neutral did not work. it did start after multiple attempts to start it in neutral, though. i assumed that the problem lay in some manner of neutral safety switch, so I went down to the parts store and procured the aforementioned switch for the vehicle, as well as a copy of how to change the switch from the service manual in the public library. well....get down to business--the car does not have any manner of neutral safety switch on the transaxle. an opened service manual for the impala at the parts store revealed that the two holes in the transmission were for some manner of safety switch, but none was there (or was ever there). the manual says that 2003 on impalas have this function integrated into the security system, but, of course, this is a 2001. is there any chance that maybe the brake switch has something to do with this issue? i'm somewhat certain that this may have made a difference, what with her likely leaving her foot on the brake in some instances (and in others, not). there is an issue with gm cars not cranking because of the lock tumblers and the security system, but an obdII scan did not show the applicable code. any gm people out therer? thanks in advance.

[icesoft]

Is there a switch located on the shift linkage on the transmission (should have 2 or 3 connectors attached to it, like a 4 pin and an 8 pin or something)? The listings I have show the switch used on 2000 and 2001 Impalas, I'm not sure what they use for a 'Manual lever position switch' on the newer models. Are you sure it's not a 2002?

Other issues to look at are the starter and associated wiring. Is the security light on when it won't crank?

[Bin_jammin]

From Identifix:

2001 Chevrolet Impala 3.4L, Vin E



Mileage: 78000



Customer Concern: No start and the security light is flashing.



Tests/Procedures: 1. Test the Passlock sensor signal wire voltage at the Body Control Module (BCM) terminal B4 Yellow wire during the problem.

2. Test the Passlock sensor power at terminal C White wire ignition power and ground at terminal B Black wire at the Passlock sensor during the problem. Terminal A is a Yellow signal wire.

3. If the Passlock sensor signal voltage sequence is consistently repeatable, and the scanner shows different/inconsistent voltages, test the BCM powers and grounds, replace the BCM.

4. If the Passlock sensor signal voltage is inconsistent and the sensor power and ground is consistent, replace the Passlock sensor.



Potential Causes: Passlock sensor circuit(s)
Passlock sensor
BCM

** Confirmed Fix **
BCM




Tech Tips: If the Passlock cylinder is replaced, a relearn procedure will need to be done by turning the key on and tapping the start position, leave the key on 10 minutes, shut off 10 seconds, repeat this 2 more times and on the 4th time the engine will start.

[Bin_jammin]

And another from Identifix:

Symptom: Possible no start, no crank or intermittant no start and trouble code P1632.



System: Body/Chassis Electrical, Emissions/PCM/Fuel



Codes: P1632



Problem: The lock cylinder housing and the rotating lock cylinder are defective, affecting the fuel enable circuit in the computer causing the no start and trouble code P1632 to set.



Test & Fix: Access the Passlock sensor 3-wire connector, located in the ignition lock cylinder housing. Leaving the connector plugged in, check for 12 volts on the White wire and 0 volts on the Black wire. This is the power and ground provided by the Body Control Module (BCM). Disconnect the 3-wire connector and verify that the BCM is sending out a 5-volt reference on the Yellow wire. If any of these voltages are incorrect, check for a problem with the wiring or BCM. Plug the connector back in. During cranking, a resistor in the Passlock sensor will drop voltage on the Yellow wire. Verify that the voltage always drops to the same level. If not, replace the lock cylinder housing and lock cylinder. Perform the relearn procedure. NOTE: Voltage drop on the Yellow wire will be different for each vehicle as there are 10 different possible resistor values. In some cases, this problem is too intermittent to test. If that is the case, the most common cause is a defective lock cylinder housing and the rotating lock cylinder.













Basically, there's a ton of confirmed fixes for this problem, and they're mostly Passlock sensor. A couple others are BCM.

[94_e34_525i]

With all do respect to your moms car this is why I don't bother with American cars, in my experience they always have electrical issues. Kiss French, Drive German. :D

[ryan roopnarine]

Is there a switch located on the shift linkage on the transmission (should have 2 or 3 connectors attached to it, like a 4 pin and an 8 pin or something)? The listings I have show the switch used on 2000 and 2001 Impalas, I'm not sure what they use for a 'Manual lever position switch' on the newer models. Are you sure it's not a 2002?

Other issues to look at are the starter and associated wiring. Is the security light on when it won't crank?

as far as i can tell, there's no switch located on the linkage. just a screw/arm entering the tranny case, leading to a cable that goes through the firewall. the car "fixed" itself the first time i got her to start it in neutral, and no codes are stored in the memory, so i don't really think that it is the tumbler that is causing the problem.

ps...no security light ever flashed. i know that chevy trucks (s10 and whatnot) often suffer from park position start problems, so the idea isn't out of the realm of possibility for me.

[Bin_jammin]

According to Identifix, you won't always have a code with the passkey module failing. Just FYI

[attack eagle]

Also be aware that on many Gm vehicles there is no actual start position wire... it is ecu controlled. The ECU monitors the drop in voltage on accessory with full voltage on ignition when the key goes into start position, and decides itself whether or not to engage the starter based on other inputs. They are wierd so a no start could be caused by anything including the ECU itself, the security system, etc. I hate to say it but take it to a dealer... they can actually see what its going on with the computer when it isn't starting.