Yeah I got a a weird one. I had a truck come to the shop with a dead injection pump (P1688 and P1689). It got a new Injection pump and lift pump from Vulcan Performance. After getting it running the WAIT TO START light is stuck ON even while driving. The grid heater are cycling as normal and canceling out either by time or by speed. I've done my AC noise check on the alternator and it was .260 at the highest. So the alternator was replaced and the new one is floating about .040 which is OK. But still got a stuck WAIT TO START. I check all the wiring for loose connection or pinched wires. I even call a local computer expert and they are stumped.

Better that than not come on as I am experiencing  .

Doesn't the IAT temp sensor output the signal and control the lamp illumination? Is there a possibility the wires for it are being shorted to ground causing it to remain on?

Already checked the wiring under the hood and didn't find anything shorted or pinched. ECM is in direct control of the light.

 

Have a look at this, from page 903 in the 2001 Version of the FSM, the WTS light and Brake indicator light do share a line of some type in the cluster itself.  Is it possible the brake indicator is back feeding?

Edited February 26, 201510 yr by AGPTurbo

Have a look at this, from page 903 in the 2001 Version of the FSM, the WTS light and Brake indicator light do share a line of some type in the cluster itself.  Is it possible the brake indicator is back feeding?

 

Right on. That different from mine but it might give me a clue to resolving this customers WAIT TO START light issue that cropped up. I'll let you know tomorrow if it helped our not.

 Disconnect orange/black wire pin #37 from ECU, Does light go out? If yes, bad ECU. If no, Ohm test that orange/black wire that runs from pin #8@ the instrument cluster to pin #37 @ the ECM and see if it's grounded. If yes, repair wire. If no, problem in instrument cluster circuit board.

Sad but true there is no shorts in the electrical I did find the connector above the valve cover and disconnected and tested. The light goes out. So I check for shorts to ground none found. But the ECM commands the ground at key on and doesn't release so that test me the .260 AC Volts from the failed alternator ate the ECM also. So for band aid fix I unplugged the WAIT TO START light lead and cleared the codes. Everything works fine just no WAIT TO START light. Not even a P0381 code which tell me the ECM has internal issues too.