Engine codes P0122 and p1406

1994 CHEVROLET S-10
60,000 MILES • 4.3L • V6 • 4WD • AUTOMATIC
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
These two codes keep coming back. I replaced TPS and IAC no fix. I replaced EGR no fix. New ECM fixed for a few days then came back. I was told by fellow tech to change main speed sensor which made sense because it was shifting odd, so I changed it fixed issue for about a month. Now it is back again. I am a tech and have followed to the letter all flow charts and done everything. I truly believe I am on the right track with speed sensor. Maybe exciter ring in transmission that speed sensor reads off? Do I need to re-flash computer again? I am really scratching my head here.
Oct 4, 2018 at 4:34 PM
Advertisement
Avatar
ASEMASTER6371
  • CERTIFIED EXPERT
  • 52,796 POSTS
Good morning

What is the exact issue you have?

1994 cannot be reflashed. Are you sure you gave us the correct information? 122 and 1406 are for OBD 2 and the information you gave us is an OBD 1 system.

Roy
Oct 5, 2018 at 3:31 AM
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
My bad 1996. I am working heads on a 1994 the s10 is a 1996, OBD2.
Oct 5, 2018 at 7:16 AM
Advertisement
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
The exact issue is a p0122 TPS circuit low voltage keeps popping. The engine idle all over the place, shifts really hard, idle sometimes to 2,800 rpm. Had to shut down the EGR code 1406 pintle pos. circuit I believe is secondary to TPS trying to fix first even though I tried a new EGR valve all circuits, signal voltages and references were good.
Oct 5, 2018 at 7:26 AM
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
These two codes are all that are present and come together to the party like a couple. And by the way Good Morning to you too.
Oct 5, 2018 at 7:36 AM
Avatar
ASEMASTER6371
  • CERTIFIED EXPERT
  • 52,796 POSTS
LOL. I hear you.

What is the TPS voltage at idle? It should be .5 to .75 volts. Make sure it rises smoothly up to 4.8 volts with the throttle open.

This will affect how the transmission shifts as well.

Roy
Oct 5, 2018 at 8:09 AM
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
Voltage is right on .48 .5____4.8. But when disconnecting TPS and jumping signal wire and reference wire voltage was almost 5 volts that is why I replaced the VCM. Just wondering if I should use genuine GM parts instead of Napa.
Oct 5, 2018 at 8:43 AM
Avatar
ASEMASTER6371
  • CERTIFIED EXPERT
  • 52,796 POSTS
No, that is correct. It is a 5 volt reference voltage. You just jumped it and it should be 5 volts because it has no load.

With the TPS connected, it only goes to 4.8.

Roy
Oct 5, 2018 at 9:26 AM
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
Correct, but on flow chart it says disconnect TP sensor plug and jump with wire sensor signal and 5 volt circuits if greater than 4 volts replace VCM.
Oct 5, 2018 at 11:29 AM
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
You know I am sitting here thinking of what you said, feeling a little stupid now I am at a loss totally just going to start over start with EGR issue and then go back to the TPS.
Oct 5, 2018 at 11:45 AM
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
If sensor is unplugged there would not be a losd but like I said I am starting over.
Oct 5, 2018 at 12:17 PM
Avatar
ASEMASTER6371
  • CERTIFIED EXPERT
  • 52,796 POSTS
Okay, let me know if you have any other questions.

Roy
Oct 5, 2018 at 1:06 PM
Avatar
SMITHSONSAUTO
  • MEMBER
  • 9 POSTS
I appreciate your time.
Oct 5, 2018 at 2:26 PM
Avatar
ASEMASTER6371
  • CERTIFIED EXPERT
  • 52,796 POSTS
Never a problem.

Always glad to help.

Roy
Oct 5, 2018 at 2:44 PM