2004 chevy monte carlo 3.4 cam sensor 12 volt pull up design?

Don't know if pull up or pull down. No signal listed on scan tool. P0341. 12 volt Power and ground good.

hi try measuring voltage plugged in and unplugged

No voltage either way but don't know if there is a circuit problem causing no voltage from pcm if it is a pull down circuit.

Pretty sure it's a pull up circuit. Do you have access to OEM scan data? If so, you can use a test light to B+ and simulate the CMP signal while watching the CMP count data.

If not, it may be time to pull the P/S pump and inspect the wiring. This video shows what can happen to the harness, if you haven't seen it already:

HUH CANT FIND A SCHEMATIC ON BBB FOR CAM SENSOR

chief eaglebear wrote: HUH CANT FIND A SCHEMATIC ON BBB FOR CAM SENSOR

They hide it in the 'Fuel Controls' diagram. Love BBB - hate how they organize their diagrams. :silly:



Even the OE diagram doesn't how how the 12V feed to the CKP and CMP are shared internally. :lol:

Good power and ground to sensor no signal on scan tool cps replaced wiring from cps to pcm good.

These CMP and CKP 'A' are both Pull-up by design.

The diagram does show circuit design. ALL GM wiring diagrams are at a state of 'off' or 'rest'.

Knowing that, 12 volts from the PCM goes in the sensor to power it, on the RD/WT wire. When the transistor is 'off' and the sensor is plugged in you'll have 12v on the signal wire.

When the transistor turns 'on' the switch(gate) on the low reference closes and pulls the signal to GND plugged in.

Therefore, unplugged there will be no voltage present on the signal wire.

Also, when you see this inside the PCM on a GM diagram...

... it is PULL-UP design.

And when you see this inside the PCM on a GM diagram...

... it is a Pull-Down design.

Bypass test worked with engine running. Seen counts on scan tool. Trying to find video Paul did at body shop with bad tone reluctor wheel. Thanks guys for all your help.