Attention: TDR Forum Junkies 
Alarm in my 2001 diesel 4wd pickup goes off once every week or two when I unlock the truck with key, more often I think when the truck has been sitting for more than a couple of days.
Neighbor behind me also has a 2001 diesel like mine; he has the same problem (his alarm goes off at 5am when he leaves for work once every week or two). That's what made me wonder if this is a common problem.
Observation: the alarm activates if you lock the truck and a person inside lifts the lock button on the inside, or if you lock truck with the window rolled down & reach in to unlock the door without the key. So, the alarm must be designed to tell its being unlocked without a key. Theory: could something be causing the alarm system to detect the tamper (lifting of the lock button) before the indication of the key turning (real key, not a tamper event) reaches the alarm? There must be two different contacts on the lock mechanism, I suppose; this is worth checking out.
I've wondered if the alarm is entering some kind of "sleep mode" after truck has been sitting for a while. Or after the computer detects the battery voltage dropping (cell charger and mobile radios in my truck could be draing the battery a little bit).
While in sleep mode, the alarm's microprocessor would wake up to samples the alarm inputs less frequently. This is pretty common in battery powered microprocessor systems. The less frequent sampling of the alarm contacts could cause the alarm to think there's a tamper event before it detects that the key is being used to unlock the door, maybe (this would be a BUG).
To test this, I started always turning the key in the "lock" direction first, then in the "unlock" direction when I unlock the truck. So far, the alarm has NEVER gone off when I unlock the truck this way. Theory: turning the key to "lock" might "wake up" the alarm system, preventing detection of the erroneous tamper event.
This is a start... possible next steps:
* see if there are really two contacts & wires back to the alarm computer (check the service manual)
* is there any chance there's a TSB on this? firmware update that addresses this?
* figure out a way to watch the computer, tell if/when its going to sleep... maybe there is a pull up voltage on the ungrounded side of switch contacts in the door lock mechanism when the computer is awake, and none when it is asleep?
* see if the computer goes to sleep sooner if you leave the headlights on. see if you can reliably make the false alarm trip occur by leaving the headlights on for a few hours?
I wonder if this is a pretty common problem. Unless someone chimes in with a known fix (from a friendly Dodge dealer???) its probably up to us to figure out how to reproduce this.
Is anybody else out there having this problem?
Rob
2001 Dodge Quad Cab short bed, Diesel, Tow package & heavy duty alternator, 4wd, LSD. Stock except for several ham radios and a warn winch. Cell phone charger is usually plugged in too.
Neighbor behind me also has a 2001 diesel like mine; he has the same problem (his alarm goes off at 5am when he leaves for work once every week or two). That's what made me wonder if this is a common problem.
Observation: the alarm activates if you lock the truck and a person inside lifts the lock button on the inside, or if you lock truck with the window rolled down & reach in to unlock the door without the key. So, the alarm must be designed to tell its being unlocked without a key. Theory: could something be causing the alarm system to detect the tamper (lifting of the lock button) before the indication of the key turning (real key, not a tamper event) reaches the alarm? There must be two different contacts on the lock mechanism, I suppose; this is worth checking out.
I've wondered if the alarm is entering some kind of "sleep mode" after truck has been sitting for a while. Or after the computer detects the battery voltage dropping (cell charger and mobile radios in my truck could be draing the battery a little bit).
While in sleep mode, the alarm's microprocessor would wake up to samples the alarm inputs less frequently. This is pretty common in battery powered microprocessor systems. The less frequent sampling of the alarm contacts could cause the alarm to think there's a tamper event before it detects that the key is being used to unlock the door, maybe (this would be a BUG).
To test this, I started always turning the key in the "lock" direction first, then in the "unlock" direction when I unlock the truck. So far, the alarm has NEVER gone off when I unlock the truck this way. Theory: turning the key to "lock" might "wake up" the alarm system, preventing detection of the erroneous tamper event.
This is a start... possible next steps:
* see if there are really two contacts & wires back to the alarm computer (check the service manual)
* is there any chance there's a TSB on this? firmware update that addresses this?
* figure out a way to watch the computer, tell if/when its going to sleep... maybe there is a pull up voltage on the ungrounded side of switch contacts in the door lock mechanism when the computer is awake, and none when it is asleep?
* see if the computer goes to sleep sooner if you leave the headlights on. see if you can reliably make the false alarm trip occur by leaving the headlights on for a few hours?
I wonder if this is a pretty common problem. Unless someone chimes in with a known fix (from a friendly Dodge dealer???) its probably up to us to figure out how to reproduce this.
Is anybody else out there having this problem?
Rob
2001 Dodge Quad Cab short bed, Diesel, Tow package & heavy duty alternator, 4wd, LSD. Stock except for several ham radios and a warn winch. Cell phone charger is usually plugged in too.
