I'm out of ideas on this and needing some help.
I continue to get and engine light and these three codes after a few miles.
1. DMTL Heater power stage
2. Lamba sensor upstream catalyst bank 1
3. Lambda Sensor upstream catalyst bank 2
I have replaced all 4 oxygen sensors, new coils, wires and plugs. And a new MAF sensor.
The truck otherwise seems to be running strong however there is a slight acidic smell in the exhauhst. It does not smell like antifreeze.
What causes the heater power stage fault?
Any ideas?

 

I too am having this problem and have replaced the o2 sensors.

I note that according to the wiring diagram, the DMTL unit and all four 02 sensors share a power wire from the fuse box (brown with a pink line) and are all powered via fuse #2 (which seems to power most engine sensors). I have yet to prove this has anything to do with the problem but is an avenue to explore...for me, the engine service light comes back on from cold start with codes cleared in three to five miles, after things are starting to get toasty in the engine bay, suggesting an iffy connector somewhere, maybe?

Doing a bit of reading on the Bosch DMTL units, they, in theory (maybe only in certain cars?) run their tests only under certain conditions: engine off, tank not too full or too empty. Again, in theory, it should take two failed tests to trigger a fault, but who knows.

 

Just wanted to note after clearing the codes, the next drive doesn't seem to trigger the codes until after a "key off" event, and then it's about a mile of driving after that. For example, drive from my shop to the park to walk the dog, about five miles away. No SES (check engine) light. Park, come back to car within an hour, start up, no SES light...drive away, about a mile away light comes on.

My codes are always

• DMTL Heater Power Stage
• Lambda Sensor Upstream Cat Bank 1
• Oxygen Sensor Heater Upstream Cat Bank 1
• Oxygen Sensor Heater Upstream Cat Bank 2

Seems suspicious to me they mostly involve the heater circuits (which I wouldn't think would be needed on a hot start, but would maybe on the cold start on the outbound leg of my trip?). As mentioned, all of those heater circuits are electrically contiguous with each other, according to the wiring diagram. Maybe a short internally in one heater would trigger all 3, or maybe there is a wiring fault which manifests when things get hot. But why only after the restart?

I probably need to do some more rigorous testing.

 

Have you confirmed good battery and charging system. All testing is moot if you don't have good battery. You WILL get spurious faults with low voltage.

 

I have 13.5 static and 14 dead even when idling at the battery, so I think the charging is ok...knock on wood.