2006 Hino Dutro Hybrid — Driveability Challenges

Taurayi Owner/Technician Harare, Zimbabwe Posted   Latest  
Case Study
Heavy Duty
P0088 - Fuel Rail/System Pressure - Too High Bank 1
P0093 - Fuel System Leak Detected - Large Leak
P0269 - Cylinder 3 Contribution/Balance
C0278 - Abnormality In Disconnection Of Brake Solenoid Relay
C1241 - Abnormality In Abs Power Supply Voltage - Active
C1249 - Abnormality Of Brake Stop Light Switch - Active

Hi Guys, 

Today I was working on MY2006 HINO DUTRO HYBRID model VF with an N04C-TE 4-cyl inline, electronically controlled diesel engine. This Engine is equiped with an Electronic Controlled Variable Geometry Turbo. Mileage on this vehicle is 298077km / 185216miles . 

The customer's concerns were that the vehicle lacks power and idles rough and un-driveable. Interviewed the driver and the owner of the vehicle and came up short of information that could help me in my diagnosis. The owner bought 4 same trucks with this particular vehicle a month ago from Japan and shipped them here in Zimbabwe, Africa.

My next step was to hook up a scan tool to pull up some DTCs that could help me get started on this vehicle problems. The codes are as follows:

  • P0088 ( Abnormality in fuel control) Active
  • P0093 ( Abnormality in fuel leakage) Active
  • P0269 ( Abnormality in injector #3) Active
  • C0278 ( Abnormality in disconnection of brake solenoid relay)
  • C1241 ( Abnormality in ABS power supply voltage) Active
  • C1249 ( Abnormality of brake stop light switch) Active

Next I started the engine and selected fuel compensation control Pids using Live Data Stream on my Scan tool. As you can see on my first Caption of a Screenshot below, the ECM has maxed out on positive fuel compensation command @ 10mm3/ 10uL for Injector for Cylinder #3. That's our first problem there pointing out to an injector not delivering fuel when commanded to. In for Cylinder #4 is opposite what is happening to Cyl #3 as the ECM injector compensation command is maxed Negative (taking away fuel) pointing out to an injector possibly stuck open. Notice higher than normal Fuel Rail Pressure @44Mpa as the ECM tries to compensate for fuel system leak through stuck open injector #4. That's our second issue there. Next, I did cylinder balance test to see if the injectors are doing their thing and BOOM!!! Injector for Cylinder 3 and 4 are not causing any change in RPM speed when commanded off using scan tool active tests option. 

Next step was to check for TSBs for lack of power for this vehicle and couldn't find anything of any help with vehicle current issues.

So, little literature on the operation of this vehicle. The truck is a Mild Series Hybrid. It has one Motor/Generator ( MG ) that is used in conjunction with the Internal Combustion Engine ( ICE ) to power the vehicle and uses 288 volts High Voltage Batteries consisting of 38 modules. The vehicle does not have a convensional starter motor it uses MG instead. The MG provides torque assists to the ICE but will not power the vehicle independently.

Back to my next step in diagnosing this "lack of power" concerns. My focus now is to find what is right with this truck to find what is wrong with it. I know that we need correct Timing, Fuel and Compression for a successful combustion which will translate to Power. Already we have fuel delivery issue as we have seen after doing cylinder balance test. On a conventional vehicle I could have used cranking current to test for relative compression test, unfortunately with this vehicle it's not going to be as easy as that, "NO STARTER MOTOR" to do that.

It's time to step-up a bit and bring out the "Big Guns". Pulled up my 4 channel Picoscope, hooked my Pressure Pulse Sensor to exhaust tailpipe to measure exhaust pressure pulses and another one to the engine dip stick tube to measure crankcase pressure pulses. I am going to use these to two signatures and a third channel with Amp clamp connected to one of Cyl #1 injector wire as sync for verifying cylinders contribution.

One would say why couldn't I have used a scan tool and command the ECM to do compression test with a conventional gauge. Unfortunately this vehicle does not have that option. On the other side it's fortunate that we can take exhaust and crankcase pressure pulses signatures and use them to get more information that a conventional could not give us.

As we can see on CAPTION #4, we have some cylinder contribution problems mostly on cylinder #3 and 4. On cylinder #4 we can clearly see a BIG FAT BURN on exhaust pulses confirming excessive fuel was delivered. This and maxed out Negative fuel compensation command suggests a stuck open injector. On cylinder #3 exhaust pulses we can see negative pulses suggesting a cylinder not combusting due to lack of fuel delivery from a suggestive stuck closed injector. This is also backed up by fuel compensation command positively maxed on this Cyl #3.

We can also see excessive cylinder blow-by on crankcase pressure pulses compression stroke for Cylinder #3 which confirms to that indeed Cyl #3 is not combusting. When no fuel is delivered in a cylinder that cylinder's crankcase pressure leak will be seen on its compression stroke. 

Next I took cylinder #3 injector voltage vs injector current signatures to verify further if indeed the injector is malfunctioning. As you can see in CAPTION #6, the injector is drawing higher actuating current than normal and also the injector open voltage for both Pilot and Main Injection is very low 22v for Pilot and 48v for Main Injection respectively. 

OPERATION of this Two-Way Valve Injector; the ECM sends injector firing signal to EDU, in turn the EDU (DC/DC Converter) will convert low system voltage to High Voltage 85v to 110v to operate opening and closing of the injector. We this information gathered I was convinced the vehicle needed New injectors , as the injection control system was doing its JOB but the injectors were not responsive.

After installing all new 4 injectors and fuel filters as well new oil and filter, the vehicle runs FANTASTIC.

Went on to verify my FIX with first, Live Data Streaming on Fuel Control Pids as Shown on a Screenshot from a scan tool. Now fuel compensation PIDS are all @ 0.00mm3/st, Fuel Rail Pressure 30Mpa, Engine idling smooth around 630rpm.

CAPTION #5 now showing Exhaust Pressure Pulses almost EVEN and GOOD for every cylinder and Crankcase Pressure Pulses still showing some blow-by due to engine-wear probably by running a longtime with malfunctioning injectors. Lastly CAPTION #7 now showing a Good working injector, as we can see injection voltage normal around 105Volts for both Pilot and Main Injection with Injection Current around 10amps.

I hope someone can Learn a thing or two from this case study. Jim Morton I know you used to work on Diesel engines for Drilling Rigs when you were 18yrs to 22yrs, I can learn more from you my FRIEND you still GOT IT!!!

Chris Diagnostician
Lansdale, Pennsylvania


Excellent write up, I really enjoyed it. I'm going to spend some time analyzing your waveforms and learning.

I hope to see more of these case studies coming along soon.

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Taurayi Owner/Technician
Harare, Zimbabwe

Thank you Chris , that's the whole reason why we share this stuff so that we can learn from each other . Hope to post more!!!

+1 Ð Bounty Awarded
Albin Diagnostician
Leavenworth, Washington

Very good case study. I like the diagnostic approach you use with both your scan data, Scope captures and logic. If you want to get the scope captures, (intake, Exhaust & crank case pulse) without the engine running, you can unplug the injectors to prevent it from starting.

This sounds like an interesting vehicle.

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Taurayi Owner/Technician
Harare, Zimbabwe

Albin , this vehicle uses Motor/Generator to crank the engine at 1200rpm . Its virtually impossible to do cold cranking tests .

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David Owner
Metter, Georgia

I enjoyed the conclusive write up. I was wondering what software you are using to make those notations. I noticed something like CVW+ on the top of the window. Is that what it is?

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Zachary Mobile Technician
Austin, Texas

You're right it does crank with the Motor/Generator but wouldn't you effectively get cranking waveforms (albeit at higher rpms than a conventional set up) if you unplugged the injectors as Albin suggested and then tried to start it? No fuel no combustion right? In any case, thanks so much for sharing this case study Taurayi. Excellent diagnostic approach which paid off big time. 

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Taurayi Owner/Technician
Harare, Zimbabwe

Zachary , let me explain how this works . The ECM sends cranking signal to High Voltage Control Module after receiving a feedback signal with injection verification from EDU. So the cranking is not constant, so after everytime the feedback signals for all 4 cylinder injection events are sent the cranking momentarily stops . The cranking process is then attempted again and again if the request for start-up from the driver is still being sent to the ECM . Lets not forget that we dealing with a Hybrid, one of the highest priority for this system is to MAINTAIN high Voltage Batteries CHARGED .So the cranking strategy is done in accordance with these HIGH PRIORITY systems in mind . To answer your question "No we can't get any useful information on cold cranking tests on this particular system" . If i find some free time to post some waveforms i took trying to do some cold cranking tests, i will post them right here . I hope my explanation makes sense . Thank you .

+2 Ð Bounty Awarded
Zachary Mobile Technician
Austin, Texas

Yes that totally makes sense Taurayi. The ECM doesn't see those verification signals from the EDU due to the induced open circuit and thus doesn't continue cranking correct? Thanks for the clarification. Yes please do post those captures if you get the chance. Thanks again for your post. 

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