Honda Insight Forum banner

101 - 113 of 113 Posts

·
Registered
Joined
·
887 Posts
This is probably not the place to ask my question but I haven't been on the site since it has been changed and having trouble navigating it. I typed in BCM problems and wound up here.
I bypassed my IMA a year or so ago just using the end plate and the BCM. It keeps the 12v batt. charged but it is time to smog it and I have a check engine light on and the code says my BCM connection is bad. I unplugged all of the plugs and plugged em back in but that didn't fix it. I am thinking about buying one and just trying it but having trouble finding one. Anybody have ideas to help me?
How did you bypass the IMA? Did you install an Arduino? If not, that is what you need.

 

·
Linsight Designer
Joined
·
1,899 Posts
Discussion Starter #102
I was thinking that the PWM signal is equivalent to a voltage, in this case between 0 and 5 volts. But that doesn't seem to be true. Is this right?
PWM itself is not a DC voltage... many signal inputs that use PWM use a simple lowpass filter that converts the duty cycle to an analog voltage. However, the DCDC doesn't have said filter, and so putting an analog voltage on it won't work. You need to generate an actual PWM signal

If I can produce a 10Hz PWM at 10-90% duty and feed it to the DVCT pin (+ output to DVCT, - output to any ground, maybe the BLU/WHT SG10 GND?), will that allow me to adjust DCDC output voltage within whatever range it can do?*
Yes. If you also want 12.x mode, you'll also need to be able to pull WHT/GRN high/low.

I recommend using an Arduino Uno... it's open source and maybe five lines of code to output a PWM signal.

I saw very slow changes when I shorted DVCT to ground - it jumped up to 15.1V, but then took at least a minute or so to drop back down to ~13.8V once the short was removed...
Yes, the DCDC adjusts very quickly in one directly, but very slowly in the other. Expected behavior.
 

·
Linsight Designer
Joined
·
1,899 Posts
Discussion Starter #103
If DVCT at the DCDC side is already 5V when the line is cut (i.e. cut DVCT, measure voltage between DCDC end and ground), doesn't that mean the output voltage is already as low as it can go?
DVCT will NEVER remain 5 volts (i.e. 100% PWM signal). Valid OEM signals are from 10% to 90% duty.
 

·
Registered
Joined
·
6,843 Posts
DVCT will NEVER remain 5 volts (i.e. 100% PWM signal). Valid OEM signals are from 10% to 90% duty.
That's what I measure between DVCT on the DCDC side and ground, with the wire to the ECM disconnected.
 

·
Administrator
Joined
·
11,777 Posts
That's what I measure between DVCT on the DCDC side and ground, with the wire to the ECM disconnected.
That may well be the case in these circs as it probably has a pull up resistor to 5v inside for fault detection or to prevent it floating...
 

·
Registered
Joined
·
6,843 Posts
^ That's how Mudder described it earlier, in another thread. He said there's a 100k pull-up in the DCDC. I had thought, though, that the 5V came from the ECM side...

So, if there is this 100k pull-up and I measure 5V on the DCDC side of DVCT, with ECM side detatched, while the signal from the ECM is a 0-5V 10Hz 10-90% PWM, doesn't that mean the DCDC output voltage is as low as it can be adjusted via DVCT - when it's not connected to the ECM? I.e. the PWM would have no way to pull the signal higher, 5V is the max and thus the minimum DCDC output voltage?
 

·
Linsight Designer
Joined
·
1,899 Posts
Discussion Starter #107
Let's take a step back and look at the DCDC's wire harness (this is the DCDC's complete pinout).

These signals aren't compicated and certainly aren't terribly interesting:
BLK/YEL: +12V when key is on.
BRN/WHT: IMSSYST, this signal illuminates instrument panel battery light (light on when DCDC pulls this signal low).
BLU/WHT: SG10, essentially engine ground, referenced to a single node inside MCM.
BLK: EGND, engine ground.
YEL/BLU: TDV, DC-DC Temp. This is a static (DC) voltage output from the DCDC to tell the MCM how hot it is. The MCM uses this information to decide when to turn on the PDU fan.
(Thick) WHT & BLK wires: high current 12 volt output, bolted to the DCDC.
(Thick) ORG & BLK wires: high current HVDC input, gray connector on junction board.

These signals are interesting for our discussion:
WHT/GRN: DVC, controls DCDC output voltage mode. Open collector in ECM, pulled up inside DCDC. '14.x' mode when high, '12.x' mode when low. Purely digital signal (not PWM or analog).
GRN/BLK: DVINH, MCM uses this signal to enable/disable DCDC. 5V enables DCDC. 0V disables DCDC. This signal is always high, unless MCM thinks IMA system is super-dead, and also for a couple seconds while starting. At all other times this signal remains high.
RED/YEL: DVCT, engine coolant temp (0:5V PWM @ 10 Hz). Open collector in ECM, pulled up inside DCDC.

...

So, to power the DCDC on a bench, we have to connect:
(Thick) HVDC input, and;
(Thick) high current 12 volt output, and;
+12V (BLK/YEL), and;
ground (BLU/WHT).

That's it. In this configuration, all other signals are left floating. Since these signals are either:
-open-drain outputs (things the DCDC controls (but doesn't know or care if it's actually connected to said things)),
-or they have a 100 kOhm pullup (inside the DCDC).

In this configuration:
-DVC is pulled to 5V, thus the DCDC is in '14.x' mode (where battery temperature is able to adjust output temp).
-DVINH is pulled to 5V, thus the DCDC is enabled
-DVCT is pulled to 5V. Thus the DCDC will output whatever voltage corresponds to said signal... I'm not in front of a DCDC right now, but my memory is that the DCDC outputs ~14.4 volts. Note that this is about right in the middle of the DCDC's potential voltage output.

Note that in an OEM configuration, I have never seen DVCT exceed 90% PWM, and thus I have never seen a constant 5 volt signal... I suspect that the DCDC recognizes that the signal should be between 10:90%, and thus is defaulting to a 'safe' 14.x output voltage.
 

·
Registered
Joined
·
6,843 Posts
I finally got something together and experimented with controlling DCDC output voltage via an external PWM signal on DVCT. I bought the PWM signal generator I linked to a few posts up - pretty cool little device. Here's an image of what I set up, with PWM duty cycles vs. DCDC output voltage at battery, posted below it. All in all it seems to work as I was trying to describe: with DVCT cut, DCDC output is as low as it can be adjusted via DVCT, and then decreasing duty increases output voltage...
82989


PWM duty cycle, DCDC output voltage at 12V battery:
100, 13.85V
90, 13.85V
80, 13.91
70, 14.02
60, 14.12
50, 14.21
40, 14.30
30, 14.38
20, 14.45
10, 14.51
0, 15.13

Oh, also, BTW, if you wanted to do this or the 'WHT/GRN' wire snip, you don't actually need to cut the wires, in case you want to cleanly restore everything later. It's really easy to just pull the spade terminals out of the connector.
 

·
Premium Member
Chicago & Detroit
Joined
·
887 Posts
I was looking through the GitHub info and came across the “Always Enable DCDC” pdf. It shows the possibility for cutting two different wires, GRN/BLK and WHT/GRN. I re-read this complete thread and had a question about the wire-cuts.

The thread says, ”Also, if you've kept the MCM installed, then the MCM is disabling the DCDC converter... unless you also cut the GRN/BLK wire.

WHT/GRN= does ECM want DCDC at 14.x or 12.x volts? Cutting this wire tells DCDC "ECM wants me at 14.x volts."
GRN/BLK= does the MCM want DCDC on or off? Cutting this wire tells DCDC "MCM wants me on."

The WHT/GRN clearly increases the voltage to the 12V battery to prevent the narrow charging range. When does one cut the GRN/BLK wire? Is this related to removing the IMA battery only?
 

·
Registered
Joined
·
6,843 Posts
^ Disconnecting WHT/GRN disables low power mode (~12.2V), keeps 12V rail at minimum of 13.85V (measured at battery). So the charging range becomes even more narrow - between about 13.85V and maybe 14.2V when cold, but generally floated at 13.85V

I think the MCM disables the DCDC only when there's a problem, such as really low IMA pack voltage and/or tap voltage. For example, when I run my pack at near rock-bottom charge state and a tap's voltage drops below 14V, the MCM commands the DCDC OFF, pretty sure that's an example of the 'GRN/BLK' wire in play... The only time I think you might want to disconnect the GRN/BLK wire is if you had a putzy pack and didn't want to do a full bypass, I guess(?). I don't know, I don't really see the point, maybe mudder will give us a valid scenario...
 

·
Linsight Designer
Joined
·
1,899 Posts
Discussion Starter #112
The MCM also disables the DCDC when the key is 'ON' but hasn't previously been to 'START'. Cutting the GRN/BLK wire allows the DCDC to charge the 12 volt battery while grid charging the IMA battery (without having to first warm up the engine such that auto-stop works.

My general recommendation is to cut only WHT/GRN. No issues with doing that.

However, there are cases where cutting GRN/BLK can be useful, too (see above). Do note that this can cause CEL if you turn the key off and on multiple times in a row. The root cause is that if the DCDC converter's logic circuitry capacitors are still charged when the high voltage bypass contactor engages, then the DCDC will immediately attempt to draw current. Since the bypass contactor is in series with a bleed resistor (to prevent arcing across the contacts), this means the gigantic high voltage capacitors in the PDU won't charge fast enough, which will cause a CEL. No CEL will occur if you leave the key 'OFF' for ~5 seconds.
 

·
Administrator
Joined
·
11,777 Posts
However, there are cases where cutting GRN/BLK can be useful, too (see above). Do note that this can cause CEL if you turn the key off and on multiple times in a row. The root cause is that if the DCDC converter's logic circuitry capacitors are still charged when the high voltage bypass contactor engages, then the DCDC will immediately attempt to draw current. Since the bypass contactor is in series with a bleed resistor (to prevent arcing across the contacts), this means the gigantic high voltage capacitors in the PDU won't charge fast enough, which will cause a CEL. No CEL will occur if you leave the key 'OFF' for ~5 seconds.
Good thinking and an sneaky cause of illusive bypass contactor codes in some scenarios.
 
101 - 113 of 113 Posts
Top