VATS security relearn?

Tiny
HD1200
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 2,444,444 MILES
I put a rebuilt 5.3 engine into my truck listed above 1500. The PCM in the truck would start truck but ran poorly had codes for mass air flow sensor and MAP sensor. In addition, the voltmeter in truck was reading 9 volts. Had alternator and battery tested they were both good. It was like PCM wasn’t sending signals to alternator and maybe something wrong with signals for mass air flow sensor and map sensor.

I had another PCM for truck so I start relearn process.

Step 1 Turn the key but don’t start security light comes on for 11 minutes and turns off. I turn key off for 5 seconds.


Step 2 turn key and don’t start this is where problem starts security light comes on for a one second and then goes immediately off


Step 3 do procedure final time still same security light comes on for one second and immediately goes of try to start and turns over once and then engine goes off.

I tried the procedure several times and got exactly same results

Could this PCM I put in be bad?


Truck sat awhile while I was rebuilding engine.

What course of action should I take to resolve this?

Thanks for any help.
Sunday, May 5th, 2024 AT 8:20 PM

7 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,443 POSTS
That process is to relearn the key only. If you swap the PCM you need to use a scan tool to program it to the vehicle and then use it to reset the VATS and then you can do the relearn you tried. To do that you need either a TECH-2 or TECH 2-WIN and a pass through device and a subscription to the GM tech site. However, the issues you stated earlier sound more like bad connections. You say it sat for a while, which could have let things corrode.
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Monday, May 6th, 2024 AT 6:45 PM
Tiny
HD1200
  • MEMBER
  • 61 POSTS
Both PCM's were programmed to vehicle it’s check all connections and are good. Could it be the pass lock sensor in the housing because everything it’s doing seems to be related to security light that comes on.
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Monday, May 6th, 2024 AT 7:35 PM
Tiny
STEVE W.
  • MECHANIC
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Were both done in the vehicle? The light coming on and going off as soon as the key rotates means it is reading the key okay. So, the issue likely isn't in the PATS system but in the BCMs communications with the PCM. Do you show any communication errors between them?
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Monday, May 6th, 2024 AT 9:38 PM
Tiny
HD1200
  • MEMBER
  • 61 POSTS
Yes, I changed the ignition housing with pass lock sensors did relearn twice fired right up. Just have to get a MAP sensor only code I have.
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Tuesday, May 7th, 2024 AT 8:23 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,443 POSTS
Strange, the sensor normally shows up with the PATS light staying on when the key is used. However you got it running.
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Tuesday, May 7th, 2024 AT 3:33 PM
Tiny
HD1200
  • MEMBER
  • 61 POSTS
Yes, that’s what I thought battery low but I’m going to figure it out.
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Tuesday, May 7th, 2024 AT 3:49 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,443 POSTS
Post the MAP code as a new question (keeps Google happy) if you wish.
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+1
Tuesday, May 7th, 2024 AT 4:14 PM

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