Truck has 3rd generator on it, no charge. Battery voltage present on Gen Bat+, Bat+, and TIPM post.
Checked all wiring at PCM pins to connectors, and did voltage drop test across the power supplies.
The only discrepancies i'm seeing are:
1) Gen sense terminal on gen is showing Batt voltage, parallel to Gen Post. But when the 2-pin connector is connected and back probed, voltage is 9v. Confirmed 3v voltage drop across Batt+ and pin-2 (red/grey).
I suspected resistance in wire but continuity checked out. I pull off PCM connector and turned key on and observed the same 9v coming from the PCM male pin corresponding to pin-2. I checked pin-10 and pin-29 as they’re fused bat+ feeds and I’m getting Bat+ voltage at the connector. Are my suspicions of resistance in the PCM causing the 3v drop? Or is it getting 9v from somewhere and spitting it back out? No info online on PCM voltage specs.
2) Pin-1 is the Gen field control. The PCM uses pwm/square waves to activate field. When I tried to measure duty cycle with my dmm, I would get sporadic duty readings, never holding for more than 2 seconds. When I tried to live test the Gen duty cycle via scan tool(key on engine off) I would set duty cycle to 50% and would read sporadic readings across the range. Unsuccessful bypass with pin-1 (br/gy) to bat negative.
Scan tool states duty cycle @ 100% while running, but Gen Post pushing batt+ voltage. Target voltage is at 14.3v.
have the same problem?
Sunday, March 28th, 2021 AT 5:56 AM