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1996 Pontiac Grand Am 96 Grand Am P1629 and P1601

Tiny
BILDO76
  • MEMBER
  • 1996 PONTIAC GRAND AM
Electrical problem
1996 Pontiac Grand Am 4 cyl Front Wheel Drive Automatic

Hey guys,
I have a 1996 Pontiac Grand AM with a 2.4 4Cyl. It is my neices car and these codes are not something that I am firmiliar with so I am looking for a little information or input on it.

The car sometimes runs for 2 weeks at times it wont start at all and sometimes it dies on her while driving. I have never had the car in my presence when it fails to start so I am going off what I have been told by my neice as well as the things that I have observed.

The codes I retrieved from the code history was a P1629 and P1601. A few weeks ago while I had it in the garage and hooked to the scanner on ititial startup all the warning lights in the dash came on and when I looked at the data on the scanner all the readings were at max values or irratic readings, and as soon as I shut the car off and restarted it all the lights went out and it was fine and all readings on the data screen went back to normal.

This week it failed to start for her and later in the day when my dad tried to start the car and it did start but the tachometer was irratic even when the car was at an idle. My neice drove it to my house and she said the tachometer never worked all the way to our house. I started the car today and pulled the codes and the tach worked just fine and all the reading in the data stream seem to be at normal values in closed loop.

I know the code P1629 is for the pass1 or theft device in the car and as far as I know the pass1 will not shut down the car while driving, but only prevent it from starting initially. The code P1601 I assume is a PCM code? I know these cars had issues with the IPC but I want to lean more toward a PCM problem?

I would appreciate any input I could get! Is there a flowchart available to troubleshoot the pass1 on this car? From what I have read the IPC is the master of the theft system and it communicates with the other modules (PCM, DERM, EBCM) to complete the system.

Thanks in advance for any input!
Bill
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Saturday, March 7th, 2009 AT 4:54 PM

8 Replies

Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
P1601 is a serial communication malfunction, and p1629 is theft deterrent fuel enable signal not recieved. Start with the p1601 code first, could have a class 2 communication problem. Does the scan tool communicate with the IPC? Looking at this code it will be one of three problems, a short to ground a short to voltage an open circuit on class 2 communication or a pcm. Also Move the PCM and IPC connectors while watching the IPC to see if serial data is lost. When serial data is lost, the IPC telltales are illuminated. This is a good indication that serial data is lost to the IPC. Check for any corroded or backed out terminals at the PCM or IPC. Post back with any other questions.
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Saturday, March 7th, 2009 AT 8:42 PM
Tiny
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Brian,
Thanks! I did trace down all the grounds first and made sure I didnt have any problems with my main grounds. I then checked all the fuses with a DVOM both inside and outside in the engine compartment.

I checked the wiring at the PCM and even wiggled them and checked them for corrosion. Last night after the car had run for a few hours I pulled the steering column tilt all the way down as this is where my neice would drive the car. When I did this I noticed that there was some play in the tilt knuckle where the pins join the knuckle so I started wiggling it around. When I would push the column to the left or drivers side of the car it malfunctioned. The tach quit, theft light and all other warning lights came on in the IPC. I pulled the column back to the right and all the lights went out and the tach started working again? I did this 7-8 times.

I shut the ignition off and pulled the cover off the column thinking I would find some chaffed wires. I traced the wires from the column all the way to the bulkhead connector under the dash and found nothing. I started the car again with the cover off and now I cant get it to malfuntion. I did notice that there is a sherical sensor/solenoid on the very bottom of the steering column that has something to do with releasing the key switch to the lock position when you shut the ignition off. This gets extremely hot when the car is running? Could this have an internal short causing the heat and maybe something to do with my problem?

I have an old scan tool MT2500 and I cannot look at the IPC with this scan tool, but sometimes my motis will allow me to see the IPC on some cars. But its at work and I dont have in this weekend. However I did want to tell you that I can obviously look at the engine and transmission with the scan tool but it will not let me into the ABS or the Airbag. The scanner simply freezes up and I have to unplug it from the DLC and start over.

Any help would be greatly appreciated!
Bill
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Sunday, March 8th, 2009 AT 9:10 AM
Tiny
BRIAN 1
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Only other advise I can give is I think your on the wright track, at the bulk head take it apart an check for a bad connection or bent terminals. Also do a wiggle test, move all the wireing up/down while its doing it to isolate the problem. Try it at the IPC and connector. Its hard sometimes when using the snap on scan tools sometimes they dont communicate with all modules, the modis might its a better scan tool.I use the tech 2. As far as the solenoid at the bottom of the column thats the BTSI (Brake Transmission Shift Interlock)its normal for this to get hot. Try the above things and post back with what you find.
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Sunday, March 8th, 2009 AT 12:29 PM
Tiny
BILDO76
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Brian,
I think I got it narrowed down. Today while it was running in the garage I was wiggling the column again to try and create the problem. For giggles I guess I tapped on the ignition switch with a 1/4" drive rachet and the tach quit and the engine would stumble and almost die. It would then throw a code for the cam sensor. I know this is not the code it was throwing for the theft system, but obviously there is a problem with the ignition switch. At this point I am going to replace the ignition switch when I can get one from the dealer. (Not a fan of aftermarket electronics) I will follow up on this post in a few days when I know if it took care of the problem or not?

Once again I would like to thank you for all your advise and help. I can normally track these things down but it is always nice to have a second opinion and in this case I had no idea what I was getting into with the theft system. So thanks for your quick response and help.

Thanks,
Bill
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Sunday, March 8th, 2009 AT 5:01 PM
Tiny
BRIAN 1
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Start with code p1601, here is the flow chart:With the engine running Observe the IPC and check the following telltales for illumination:
"Â Check oil

"Â Coolant level

"Â Oil pressure

"Â Voltage

Check the tachometer and the temperature gauges (if equipped) for proper operation.
Are all the telltales ON and the gauges not operating properly?
--
Go to Step 3
Go to Step 9

3
Install a scan tool.

Can the scan tool communicate with IPC?
--
Go to Step 4
Go to Step 5

4
Check the UART serial data circuit for an open and repair as necessary.

Was a repair necessary?
--
Go to Step 9
Go to Step 6

5
Check the UART serial data circuit for a short to ground or to voltage and repair as necessary.

Was a repair necessary?
--
Go to Step 9
Go to Step 7

6
Check the PCM connector for a poor connection and repair as necessary.

Was a repair necessary?
--
Go to Step 9
Go to Step 8

7
Turn the ignition switch OFF.
Disconnect the PCM connectors.
Turn the ignition switch ON.
Attempt to communicate with the IPC using the scan tool.
Can the scan tool communicate with the IPC?
--
Go to Step 8
Go to Section 8A-50

8
Replace the PCM.

Is the action complete?
--
Go to Step 9
--

9
Using the scan tool, clear the DTC's.
Start the engine and idle at normal operating temperature.
Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.
Does the scan tool indicate that this diagnostic has ran and passed?
--
Go to Step 10
Go to Step 2

10
Check if any additional DTCs are set.

Are any DTCs displayed that have not been diagnosed?
--
Go to applicable DTC table
System OK
follow this chart first and post back with what you find.
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Thursday, March 12th, 2009 AT 4:55 PM
Tiny
BILDO76
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Brian,
Thank you so much! I found the problem. You were right from the beginning. I had realized that the floors were wet in the car but I contributed it to the fact that it has rained alot lately and my neice and her friends getting in and out of the car. Actually at one time I had checked the harness on the drivers side for any kind of damage from moisture. The problem however was that there is rain getting in through the top part of the firewall on the passengers side from rain running down the windshild and had actually saturated the Airbag module on the passengers side floor under the seat! The plug and wiring was corroded and actually so bad that I had to bust the pigtail to get it disconnected from the module.

I have pulled the carpet completely out of the car to dry everything out and I am going to have to do some sealing on top to keep the rain from getting inside! I will have to get a harness and the module and do some soldering to get everything back together. If I get a used module do I have to get it reprogrammed to work in this car? Or will it work as long as the part# is the same? Once again you have been an incredible help and I want you to know that it is EXTREMELY appreciated!

Thanks,
Bill
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Thursday, March 12th, 2009 AT 9:24 PM
Tiny
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Thats great that you found it! As far as the module, yes it has to be programmed. It does not matter if the part number is the same. Once its programmed it should work fine.
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Friday, March 13th, 2009 AT 4:08 PM
Tiny
BILDO76
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Brian,
Just wanted to add to this post in case someone else has encountered this problem. I did find the source of the rain leak and it is kind of hidden.

I took the hood off the car for easier access and also removed the wiper arms and the plastic bezel under the wiper arms. I cleaned out all the rain drians and began inspecting for any spots where possibly the sealer had pealed off. I found a little rust on the drivers side near where the electical harness goes inside the car, and the rust contined alont the front of the firewall under the wiper motor. To be sure I pulled the wiper motor off so I could see under it and that is where I found the hole. Behind the wiper moter is where one of the water drains exits and runs onto the firewall and it was right there where a whole about the size of a nickel had rusted thru the firewall allowing water to run inside.

I am sure that any type of automotive caulk or seam sealer would work, but because of the rust issues on the firewall and not being to clean it real well I cleaned it as best as I could and sealed it with POR 15. I also sealed around all other places that there might have been a possibility of water entering the inside.

Everything else is working fine! Thanks for the help!
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Sunday, March 15th, 2009 AT 10:11 AM

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