01 DTS headlights not working

[mrchristopher]

All grounds are good,fuses, and relays, checked headlight switch unit with resistance tester. Could it all be the sentinal sensor? Thinking of looping it out of the circit for tempoary night driving.

[Cadillac Jim]

Just today we had an identical complaint that turned out to be a broken wire in harness for the dimmer relay.

If you manually turn on the headlights (delay slider all the way to the left, including the detent, switch pulled out) and the headlights do not come on, the sentinel sensor isn't the culprit.

Please be more explicit. Is there anything that you do that causes the headlights to come on? Such as, short the terminals of the high/low beam relay?

Often a wiring problem will throw a code. Post your OBD II codes here and maybe that will tell the story.

[mrchristopher]

Just today we had an identical complaint that turned out to be a broken wire in harness for the dimmer relay.

If you manually turn on the headlights (delay slider all the way to the left, including the detent, switch pulled out) and the headlights do not come on, the sentinel sensor isn't the culprit.

Please be more explicit. Is there anything that you do that causes the headlights to come on? Such as, short the terminals of the high/low beam relay?

Often a wiring problem will throw a code. Post your OBD II codes here and maybe that will tell the story.

I get daylamps only when in gear. When sentinal on or off, no lights, nada.

codes are

dim b1390 c

ipm b0184 h

ipm b0189 h

ipm 2646 h

pcm p1860 c

Keep in mind I drove to work today (3mi.) without sentinal plugged in. Was replaced @12noon with new unit with no change.

[Cadillac Jim]

B1390 Device Voltage Reference Input Circuit Malfunction

B0184 Solar Load Sensor #1 Circuit Range (sunload)

B0189 Solar Load Sensor #2 Circuit Range (sunload)

B2646 Ambient Light Sensor Circuit Range

P1860 TCC PWM Solenoid Circuit Electrical

Note that the solar load sensor is part of the A/C system, not the twilight sentinel. If you unplugged it and turned on the key while it was unplugged, that would account for the B0184 and B0194. The B2646 is the twilight sentinel sensor, and again it will be set if the key is turned on while it is unplugged, or if there is some problem with it or its connections.

The Current codes are B1390 and P1860. I suggest that you address these first, then reset all the codes and drive the car, then recheck the codes and address whatever comes back.

The B1390 is serious, and it could cause other codes, including a problem with the twilight sentinel. This likely means that there is a problem with a fuse, the battery cable, or the battery. I would look at a 2001 FSM for that DTC and follow that troubleshooting chart.

The P1860 probably means that there is a loose or bad connection in the wiring harness of your transmission. You can check the TCC for continuity at the transmission connector to eliminate a bad TCC solenoid. You will need an FSM to get the connector pin-out to find the right terminals to check.

[JimD]

All grounds are good,fuses, and relays,....

In another post, you say you have daylamps only (which I expect is the normal Low beam Daytime Running Lamps).

Try this:

Twilight sentinel OFF (slider full left).

Headlamp switch ON manually.

In the underhood relay box locate the HDLP LO BM relay. Borrow a similar four blade relay from another circuit and install in the HDLP LO BM socket.

Results ??

[mrchristopher]

Thanks fellas, for replies.

Iv'e tried all combo's for switching lights on (not daylamps) unsuccesfully. Even borrowed switch assy. from neighbors dts to eliminate that.

as for all the codes likely all but the tranny one are related to the sensor not being plugged in while running car. Today pulled fuse boxes apart and separated them. not enough corrosion, or tatle-tale signs for the problem. Thinking it may be the module.

The 1860 code may be the culprit, need to get a FSM.

[JimD]

....The 1860 code may be the culprit, need to get a FSM.

After your situation is resolved, please return and tell us (me) how a Powertrain code (P1860) is related to a lighting issue.

[Cadillac Jim]

I wouldn't go changing modules or other expensive parts until I went though a diagnosis. Get the FSM now, the parts later.