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I have the same issue as the person in post http://www.justanswer.com/questions/1iati-pontiac-grand-prix-gtp-2000. My auto shop gave me the same response after fixing the wiring issue: basically they are telling me I should replace my PCM, but at a cost of over $1000, I do not want to spend that kind of money on a 7 year old car with over 110,000 miles on it. The car runs fine, just throws codes and the SES light comes on intermittently. Can I just drive the car, I don't really need the tach to work and I can live without the TCS as well. Bottom line is what will happen if I do not replace the PCM? Will I get stranded?

Submitted: 230 days and 4 hours ago.

Category: Pontiac

Value: $9

Status: AWAITING EXPERT REPLY

Posted by Pete 229 days and 21 hours ago.

Info Request

Hello,what are your code numbers that set in your computer?Does it run and drive ok are there any other issues besides the codes that have set?Thanks Pete

192 days and 17 hours ago.

Reply

Relist: I still need help. My mechanic indicates 3 codes: P0135 (bad o2 sensor), P0300 (gen misfire), P0336 (CKPS sensor) but they keep telling me they need to replace the PCM. That's $1000+ dollars! I see the P0336 as a bad crankshaft position sensor... why do they keep telling me it's a bad PCM?

192 days and 17 hours ago.

Reply

also, the car is not running fine at this point (very rich), but I guess that could be due to the bad O2 sensor.

Posted by Anthony 192 days and 17 hours ago.

Info Request

Hi!

The PCM is easy to change and dosent cost a grand. Actually they are like $300 from Autozone. Would you like the procedure to change it? Its actually under the airfilter.

192 days and 16 hours ago.

Reply

Doesn't the PCM have to be reflashed (by a dealer) as well, incurring additional costs?

192 days and 16 hours ago.

Reply

Also, does P0336 really indicate a new PCM or crankshaft position sensor? Every where on the internet I see that the P0336 indicates a bad crankshaft sensor, not a bad PCM being the cause of that code.

Is it true that the car can still run without a crankshaft sensor working? I have read that the computer would rely on the camshaft sensor for data as a substitute?

Can a bad crankshaft sensor cause the engine misfire issues I am experiencing as well.

Posted by Anthony 192 days and 16 hours ago.

Info Request

I would replace the crankshaft sensor right away. If you still have the problems from the PCM, you can buy one already flashed by giving the vin# of your car to the parts store and they will get you one thats ready to drop in. Do you want both procedures?

192 days and 16 hours ago.

Reply

Can please answer my questions from my previous post?:

Also, does P0336 really indicate a new PCM or crankshaft position sensor? Every where on the internet I see that the P0336 indicates a bad crankshaft sensor, not a bad PCM being the cause of that code.

Is it true that the car can still run without a crankshaft sensor working? I have read that the computer would rely on the camshaft sensor for data as a substitute?

Can a bad crankshaft sensor cause the engine misfire issues I am experiencing as well.

Posted by Anthony 192 days and 15 hours ago.

Info Request

The crankshaft sensor can and will cause what you descibe. However a bad PCM will say you have a bad ensor when you really don't. The best thing to do without any test equip would be to replace the crank sensor first. If the code comes back for it then you have a bad PCM. As I said earlier I can provide the procedures for both.

191 days and 21 hours ago.

Reply

Posting the PCM replacement procedure would be helpful as I am fairly certain I can do that myself (after I read the procedure to confirm :)

Replacing the crank shaft sensor seems a bit more of an ordeal with removing the marmonic balancer, etc. Is that something a home-garage mechanic can accomplish? Will I need special tool(s)? Posting that procedure would be helpful as well.

Thank you!

Posted by joshsdaddy2006 191 days and 21 hours ago.

Info Request

HI, I see Anthony has already helped you but he is currently offline. He is absolutely correct though. First test or replace the crank sensor. Reason for this is because the bad crank sensor will cause the misfire ( it affects timing) and in turn that will mess up your O2 sensor readings. And that price for the computer IS rediculous.

179 days and 16 hours ago.

Reply

What is the procedure to replace the PCM?

I have a replacement. I know where the PCM is located. I fI had to gues, I think I should I disconnect to negative battery cable. Is there anything else I need to know/do before removing the old PCM and replacing with the new PCM?

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Info Request

Hello,what are your code numbers that set in your computer?Does it run and drive ok are there any other issues besides the codes that have set?Thanks Pete

Reply

Relist: I still need help. My mechanic indicates 3 codes: P0135 (bad o2 sensor), P0300 (gen misfire), P0336 (CKPS sensor) but they keep telling me they need to replace the PCM. That's $1000+ dollars! I see the P0336 as a bad crankshaft position sensor... why do they keep telling me it's a bad PCM?

Reply

also, the car is not running fine at this point (very rich), but I guess that could be due to the bad O2 sensor.

Info Request

Hi! The PCM is easy to change and dosent cost a grand. Actually they are like $300 from Autozone. Would you like the procedure to change it? Its actually under the airfilter.

Reply

Doesn't the PCM have to be reflashed (by a dealer) as well, incurring additional costs?

Reply

Info Request

I would replace the crankshaft sensor right away. If you still have the problems from the PCM, you can buy one already flashed by giving the vin# of your car to the parts store and they will get you one thats ready to drop in. Do you want both procedures?

Reply

Info Request

Reply

Info Request

Reply

What is the procedure to replace the PCM? I have a replacement. I know where the PCM is located. I fI had to gues, I think I should I disconnect to negative battery cable. Is there anything else I need to know/do before removing the old PCM and replacing with the new PCM?

Related Pontiac Questions

Hi!

The PCM is easy to change and dosent cost a grand. Actually they are like $300 from Autozone. Would you like the procedure to change it? Its actually under the airfilter.

What is the procedure to replace the PCM?

I have a replacement. I know where the PCM is located. I fI had to gues, I think I should I disconnect to negative battery cable. Is there anything else I need to know/do before removing the old PCM and replacing with the new PCM?