I have a 2004 impala 3.4 that’s having start issues. Long story short my car started having a slow crank 2 months ago. Took it to a mechanic he was 90% sure it was the crankshaft sensor he replaced that and put a new harmonic balancer on. That didn’t solve the issue (turns out it just needed a battery) paid $340 for the sensor and balancer for nothing but of course I wasn’t getting a refund. Now the car has started having issues again it stalled on me randomly. Check engine light came on. While accelerating the car was sputtering. Had car scanned for codes P0336 came back for the crankshaft sensor. Anyone know why it could be doing this with the new sensor? Part is still under warranty so I’m taking it back to the shop Tuesday but worried this guy might not know what he’s doing. Could the sensor be faulty?
Yes. On the 3.4, there are two crankshaft position sensors. One, the 24x, is behind the harmonic balancer. That is the one your mechanic replaced.
The other, 6/7x, is on the firewall side of the motor, and it's kinda hard to get at, but can still be swapped out in the driveway.
The 24x puts out 24 pulses per revolution. IIRC, it feeds the engine computer.
The 6/7x puts out 6 evenly spaced pulses per revolution, with a double pulse at 0°, hence the 7 nomenclature. This signal goes to the ignition control module which drives the spark plugs.
I've replaced both these sensors on the 3.4. The worst part of the 6/7x was having to go back and forth between crawling under the car to do the work by feel, and then climbing back out to look down from the top to see what I was dealing with. It was a workout.
To keep dirt from getting into the engine, make sure you clean the area around the sensor before removing it. With a thin film of oil applied to the o-ring, the new one easily pops in the hole and is secured with only one screw, IIRC.
gmpartsdirect.com lists this GM part number: 10456555
Autozone.com shows this AC-Delco part: 213-148
If you poke around the Autozone site, as well as other retailers, you can get a feel for the range of prices. The lowest price I saw was $19 for a Valucraft versus a high of $46 for the AC-Delco.