OBD2 Sensors >> GM 4.3L V6 LU3 / LG3 Engine Sensor Locations

View with engine air intake installed.  2008 Chevy Silverado WT 1500 4.3L V6

  1. Fuel injectors (located under the intake manifold)
  2. Mass Airflow / Intake Air Temp Sensor (MAF/IAT)
  3. Camshaft position sensor (CMP) (located at the front of the engine above the crankshaft pulley)
  4. Oil pressure sensor (located at the top rear of the engine under ignition coil)
  5. Knock sensor 1 (KS) (located on the driver side of the engine near back bottom)
  6. Knock sensor 2 (KS) (located on the pass side of the engine above starter)
  7. Crankshaft position sensor (CKP) (located under the vehicle near the crankshaft pulley)
  8. Engine coolant temperature sensor (ECT) (located at front of driver’s side cylinder head)
  9. Ignition coil (located on back of engine)
  10. Manifold Absolute Pressure Sensor (MAP) (located on the intake manifold at the front of the engine)
  11. Heated Oxygen Sensor Bank 1 (located in exhaust pipe attached to driver side exhaust manifold)
  12. Heated Oxygen Sensor Bank 2 (located in exhaust pipe attached to pass side exhaust manifold)
  13. Throttle Body / Throttle Position Sensor (TPS)

Models Found On

  • 2003–2005 Chevrolet Astro/GMC Safari
  • 2003–2014 Chevrolet Silverado / GMC Sierra
  • 2003–2004 Chevrolet S-10 / S-10 Blazer / GMC S-15 Jimmy


There are multiple GM 4.3L V6’s.  The Vortec V6 4.3L is an earlier version with a different ignition system and fuel injection system.  This component diagram covers the later model version LU3 / LG3.  There is no distributor, and the engine has the “Spider” injection system using poppet nozzles versus electrical injectors.
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8 months ago

I have a 4.3l v6 98 bravada and I caused a coolant leak, I was testing the MAF by unplugging and driving, drove better and I drove it for to long it overheated started to whistle spew coolant in top of the engine from under the air intake tube near the throttle body it was white smoke and now it leaks from under near the front, what i think it may be is head gasket or intake.Leaks only when engine is turned on now from bottom.

7 months ago
Reply to  Rafael

Couple options:
1. Disassemble the top of the engine to see where the coolant is leaking from. Intake gaskets are common failures, but a head gasket isn’t out of the question.
Is there coolant in the oil, or oil in the coolant? That would be more common of a head gasket, but once again, I’ve seen intake leaks start to fill the crankcase too.
2. If you can pressure test the cooling system, see where the coolant is escaping at. You can sometimes see intake leaks spewing around the intake. If it is leaking from a head gasket, you may see it spraying out of the head gasket. Or it may cause the oil level to rise.

I hope these suggestions help.

11 months ago

I have a 94 gmc jimmy 4.3 2wd, there is a plug that comes off the harness along with the IAC and maf, it has 2 wires a yellow and a black and has a blue collar. Any idea what it is and the location. I can’t seem to figure it out

Nathaniel O.
Nathaniel O.
10 months ago
Reply to  Kody

Hello Kody. It goes to the engine coolant temperature sensor. It plugs in to the sensor just to the left of the alternator as viewed from the front of the vehicle.