hi all I am new here I have nice headache with me. honda civic 2008 had dc-dc converter problem then I fixed (change 2 mosfets and shotky diode) then start to work even 2 days all was good but this morning afain same things happened. shows on dashboard engine+ima and battery lights so ima system does not charge but strange thing if keeping car between 1500-2500rp 12v battery charging but ima not. so if rpm less then 1500rpm 12v battery stop to charge as well. so removed all again checked dc-dc converter all is ok mcm ima control unit wires harness fuses all looks good. setup all again uraa again start to work all system but after 5km drive on the way again all light came on dash and start to do same thing between 1500-2500rpm 12v battery charging but ima not. So what can be wrong with that car?
btw diagnostic DTC shows : "dc-dc converter low voltage"

 

Likely failed IMA battery.

When IMA battery fails past a certain point, it is isolated from the system. Once isolated, the raw output of the IMA motor at low rpm is below the minimum input voltage of the DC-DC converter. Additionally, at high rpm, the raw output of the IMA motor is too high for the input voltage of the DC-DC converter, thus charging only occurs in within a range of rpms.

Many consumer grade code readers fail to read all hybrid codes. This technique can "blink" out the codes:

https://99mpg.com/mikestips/readingtheblinkcod/

Follow the instructions and report the values returned.

 

codes:
P1570 (66)
P0A94
P1435
when short obd pins nothing show on dashboard screen just "no" was blinking that is all.btw after 3 times switched off and on again ignition ima start to charge even drive again except 12v battery ima was charging even instaned of that codes

 

P1570 = Battery module individual voltage problem

This either indicates a connection problem, i.e., one of the 12 wires used to report the 11 is broken, or the individual modules are at substantially different voltages indicating one or more cell failures.

P1435 does not turn on the IMA light
P0A94 does not turn on the IMA light
P1570 turns on the IMA light

P1435 requires investigation and resolution of ALL other DTC. This code simply turns on the red battery light indicating a charging system problem.
P0A94 may be a legit failure of the DC-DC. Check the #23 BACK UP 10A fuse in the underhood fuse/relay box.

You need to check the 11 tap voltages of the battery to investigate P1570

https://dl.dropboxusercontent.com/s/...or%20Check.png

Viewed from BACK of plug, i.e., you probe the connector from the wire side while the connector is plugged in. It may take an uncomfortable amount of force to make contact with the metal crimps on the wires. Sharp voltmeter leads help. Auto-ranging or 20V or more scale on the meter.

Record voltages to XX.XX precision if possible.

Alternatively, you can unplug it and check the other end; however, those holes are very small and may be difficult to probe. You will need to reverse the diagram to ensure you collect the correct measurements. If you measure anything over 18V, you've made an error.

Based on the DTC codes and described symptoms, I would conclude you have a failed IMA battery with a potentially failed DC-DC converter.

 

thank you for your detailed help. I will check out all wires and connectors. SO can I ask? if ima cooling fan not connected can I get the same errors?

 

No; however, unplugging the fan will essentially guarantee battery damage in all but the most mild climates. The 06-08 has the 2nd worst hybrid battery on the planet - second only to the 09-11 HCH. Cooling is critical.

 

than u so much for your help

 

hi mate I changed battery cells 2pcs for 1h on the way while drive all was good but this morning again happened same thing ima+battery+engine light stuck on odometer. check out live date so ima batteries shows total 165v each cell 15v but not increase just 165/15 thats all. now gives dtc P1575 and again same between 1100-3100rpm 12v battery charging but over 3150rpm stop the charge

 

What are the 11 votlages?

 

It sounds like there may be an underlying issue that is causing the dc-dc converter to fail. Since you have already replaced the mosfets and Schottky diode, it is possible that the issue is related to the wiring or connections in the system.