My truck stalled, then started right back up. When I put it in gear, it immediately stalled again. Now the fuel pump doesn't energize when I turn the key on, and the fuel gage reads below empty and gas light comes on, but tank is full. Tried swapping fuel relay with another - no change. I get codes 920, 921, 999 from the odometer diagnostic. Also tried to get a re-flash, but the guy said he couldn't get it to read. Is this a bad PCM?

 

Is the PCM energizing the fuel pump at initial key on? Are you getting power back to the fuel pump if it does? The pump and the gauge both failing at once would tend more toward a wiring issue, I should think. Check the harness going back to the pump. Make sure it didn't get cut/crimped somewhere.

 

The fuel pump does not initialize at key on. The pump was replaced just over a year ago.

 

If somebody hooked up some proper diag equipment and couldn't talk to the PCM it could well be a bad PCM, or at least a PCM that isn't powering up. 98 has the fully digitized cluster so all the gauges are controlled by the PCM. No PCM = no needles move.

 

I believe the fuel pump powers up thru the relays in the IPC/PDC, But I would check for power and ground at the fuel pump module and the big connector on the driver side frame rail. Make sure a wire didn't get pull out the connector.