DRL Module?

Hank, I just received my 2005 pkg 3, (no HIDs) and have been trying to find out the same thing. I have been all over the boards and there seems to be a consensus that there is a means to reprogram the ECU to allow the halogen headlights only (not HIDs due to operating constraints) to run at reduced voltage (as DRLs) when certain vehicle parameters are met. The Canadian cars operate in this mode due to law. The speculation is that there is a simple means to have the USA halogen headlight cars operate in the Canadian mode. When I called Toyota USA, I got the corporate '"it is not an option in USA modules and DRLs are not supported". When I called a local dealer, I was lucky to find a tech who was willing to look at the issue and he felt that at the least, my car would need to have a DRL relay installed and then maybe his hand-held tester would allow the system to be enabled. For all the discussion on the Prius boards, I haven't found any one who actually has done this mod. If anyone has actually been successful in this endeavor please let share your experience.

 

There are instructions in the service manual to reprogram the headlight computer to turn on DRL's. Talk to your dealer about it.

Nate

 

Thanks Nate,
Are you talking about the post that references Toyota Body Electrical-Multiplex Communication, section BE-4? That information seems to indicate that it is possible to toggle on or off the DRL function with the hand held tester, but also has an asterix that indicates it is optional equipment. The local dealer tech I spoke to seemed to think that there was some other hardware (a relay and maybe more) that would be required to allow the body ECU via the HHT to enable the DRL. Do you know of a link to the manual or other info that shows the procedure? If not, a local dealer contact (I live in Denver) that can point me in the right direction?

 

in the underhood fuse box on the right hand side have a look at fuse postion #25 and see if there is the terminals in there that would make contact with the fuse. I would guess not. But if there is it'll need the fuse and the relay and possibly the resistor assy. I'll check for the position of the relay in the day light and see what location it is.

 

Frank
Your are correct. My USA spec does not have the terminals in the fuse block for DRLs or terminals in the relay block. It appears to be a much larger task than just having the dealer reprogram the body ECU. It was a great idea, but it looks like if I want to run with lights on during the day I will have to leave them on and have the circuit controlled by the auto off feature. My only concern is running the lights at full power all the time will cause the ICE to run more and negatively impact the milage. My bet is that Toyota did not want to cause a marketing conflict in this country offering DRLs on lower package vehicles with halogens and no DRLs on the HID vehicles.

 

laserbill, I will fess up that I installed factory DRL's in a 1994 Camry. Here's the process:
1. Get the Electrical Wiring Diagram (EWD) for the headlight circuit.
2. Buy the relays and modules from a dealership, for me, I had to call Canada.
3. Buy the connectors for the modules. (Kind of tricky, best to try to find an old wiring harness laying around the dealership. Part numbers for empty connectors are in the EWD).
4. Buy or scrounge pins and wiring to go into the connectors. Part numbers are located in the wiring harness repair kit. Given their high cost, I recommend gleaning from a scrap harness. (Hint: Make friends with your local dealership!)
5. Wire everything in to match DRL diagram. Voila!
6. Step 6 for Prius: Have dealership reprogram Headlight ECU to activate DRL's.
7. Possible problem for Prius: Automatic headlight switch (on stalk) and sensor (on dash) may be required. A challenging consideration.

(Frank, does your car have Automatic headlights?)

Nate

 

the Canadian Prius 2k1-2k4 has both DRL's and the Auto feature. But if you can believe it the 2k1-2k3 doesn't have heated outside mirrors and no terminal pins in the fuse box to allow it to be retro fitted. Heated mirrors in Florida and not in Canada, you can tell the marketing people who work for Toyota don't know sheep s**t from dates.

 

lazerbill if your up to the task on the relay box upper left hand side of the firewall in the engine compartment looks like an easy task to open the wire harness and see if the terminls are just taped in the harness and not installed in the block. If they are then I would suspect that the fuse block ones are too. That would ultimatly make the whole project easier. If they are let me know and I'll cut open the harness and give you the wire colour code and positon in the block.

 

Frank
Great offer and idea. I was going to check part numbers to see if there was more than one USA spec wiring harness, but your idea is easier. I will probably be able to take a look next week and let you know. I had looked in the bottom area of the relay block in hopes that I could see extra wires but did not see any. If I can, I will take a peak under the fuse block too.

 

there will be two harness listed, one for HID and one for halogen lights. So the best thing to do is look for 3 harnesses, if there is three one will be for the CDN model with DRL's.

 

Lazerbill the next time I have my 2k3 up to operating temp and into S4 and have the miniscanner on I'll pull the fuse and give you the difference in amperage draw with DRL's and with out. I can tell you at this time with them on the amp draw is 1.78 amps nominal.

 

lazerbill the currennt draw on the HV battery with the car warmed up and in S4 and heater and radio off
headlights on low beam 1.52 amps
DRL on 1.22 amps
headlighs off (pulled fuses) .73 amps.
the fuel used to charge 1.52 amps is nill. Coasting to a stop at the end of your block will replace all the current used in having the headlights on for your daily commute.
NOW one thing to realize is the readings above are for a 2k3 Prius and how much difference there is on a 2k4 I'm not sure but I'd bet not a lot.

 

Frank
The info you guys provide on this site is awesome. I looked closely at the wiring harness that enters the relay block and it appears fatter at the terminal end suggesting that it might contain DRL and fog wiring inside. Before I split the wiring cover, I looked at the fuse block and chickened out. Even if the fuse block has DRL wiring buried somewhere in the harness, I could not bring myself to open it up and explore. My wifes baby has less than 400 miles on it and to access the bottom of the block would involve some semi serious work. That in addition to it not just being low voltage stuff gave me reason to pause. Thanks to the info you just provided, it reinforces my decision. The difference in amperage draw in DRL vs low beam is not worth the effort and risk to the warrantee. My original idea was that with a simple mod I could pick up a cool safety feature and have a "unique" USA prius. This is one of the few times that Toyota did not make it relatively easy to take advantage of their international car platforms to make changes. Unless we are missing something I will continue to be a slightly less lit Laser. Thanks to all on this thread.

 

there is no high voltage in the fuse box portion of the Prius. Just in the battery module and in the inverter assy under the hood and wire harness down to the A/C compressor. The converter which charges the 12 side of the car is integeral with the inverter. The Prius has miles of wire in it. Any terminal that you can access without wrenches and sockets will be 12Volts. If your going to check for power on any terminal in the fuse box or in any of the harness connectors PLEASE UES a volt meter and not a test light.