by Moiv on Thu, 28 Nov 2013 1:19 +0000

Hey all, the question was asked what all the data in Techstream actually means, so I went on the hunt for some explanations of the technical terms and the relevant reference values. I've also gathered information from threads all over this site, personal notes and the repair manual to determine what it could mean if the values are out of range. Although, I wasn't able to determine with certainty if the reference values for auto's are different from manuals.

Credit goes to boxhead, The Roo and other members for past input on related subjects. Credit also to the members who have posted their readings so far, they helped me to re-think some of my assumptions.

Lastly, If any explanations or reference values are inaccurate or incomplete in any way, please feel free to say so, so I can fix it. I'm only human :D.

Cheers,

Marvin

EXPLANATIONS & REFERENCE VALUES

Engine speed

Engine revolutions. Same as the instrument rev counter, only this reading is digital.

Reference: Idle - around 750 RPM, WOT - 4600 RPM

Calculate load

Indication of the amount of load in terms of airflow generated by the engine (not torque or horsepower) during idle, when towing, travelling uphill, accelleration etc. It is not measured by a dedicated sensor, but rather calculated using various parameters. The output is in percentage from the peak airflow. How it is calculated exactly is different for each manufacturer but it might include readings from the MAF, MAP, engine speed, throttle position or intake air temp and pressure sensors.

Reference: Idle - around 16%, WOT - 95% and above (peak airflow)

MAF

MAF or mass airflow is the amount of air being sucked (technical term, honest :P

) into engine measured just after the airfilter. The output is in grams per second.

Reference: 5-12 gm/sec (Idle)

Atmosphere pressure (abs)

As the term implies, it is the absolute atmospheric pressure in kiloPascals, measured at ground level. Changes with outside temperature and altitude. Pressure drops by 1 kPa for every 100m rise in altitude. The opposite for drop in altitude.

MAP

Manifold absolute pressure is the pressure measured inside the manifold just before the EGR where the feed for the sensor is located. The ECU uses these readings to determine EGR flow and boost pressure among others. The output is in kiloPascals.

Reference: 95-105 kPa (Idle)

Initial intake air temp

Snapshot of the intake air temperature at the exact moment of engine start. Measured by the sensor incorporated in the MAF meter.

Reference: whatever the temp is at engine start.

Intake air

Temperature of the air past the air filter, measured by sensor inside the MAF meter. Output in degrees Celsius

Intake air temp (turbo)

Temperature of the air entering the intake manifold (also intercooler air temp), as measured by the sensor at the intercooler outlet. Not to be confused with the intake air temp sensor housed inside the MAF, which is used for different purposes.

Initial engine coolant temp

Snapshot of the coolant temperature measured at engine start. The sensor is located just above the waterpump. Output is in degrees Celsius.

Reference: whatever the coolant temp is at engine start

Coolant temp

Actual coolant temperature with the engine running. Sensor is located just above waterpump. Engine is considered warm when coolant temp is upwards of 86 deg C.

Battery voltage

Voltage of either the battery or the charging system (alternator), depending on wether the engine is running or not. Output in Volts.

Reference: Engine off - around 12 Volts (battery), Engine on - around 13.5 Volts (charging)

Accelerator position

Position of the accelator pedal, calculated in percentages.

Reference: Idle - 0%, WOT - just under 100%

Actual throttle position

Position of the throttle valve (butterfly) in the intake manifold. Aids in smooth engine shut-off and rate of EGR. Output in %

Reference: Engine off - 0%, Idle - around 80% (open)

Throttle close learning val.

The position in which the throttle valve is considered closed by the ECU. Output in degrees (I guess, from the vertical axis of the sensor)

Reference: 17.2 - 17.5 degrees

Injection volume

The total amount of fuel being injected into the cylinders. Output is in cubic millimeters per stroke.

Reference: 5-12 mm3/st (Idle)

Injection Feedback value

The amount of compensation or correction of fuel being injected into cylinders 1 to 4. A positive value indicates fuel is being added, and a negative value means fuel is being reduced. Output is in cubic millimeters per stroke.

Reference: +/- 3 mm3/st (Idle)

Pilot 1 & 2 injection period

Duration of the pilot injection. The 1KD-FTV engine features a pilot injection sequence which is smaller in volume and shorter than the main injection. It's purpose is to reduce engine noise or knock. Apparently, there are 2 pilot injections. Output in microseconds

Target common rail pressure

Fuel pressure in the common rail that the ECU is aiming for. Output in kiloPascal (absolute).

Fuel press

Actual common rail fuel pressure. Output in kiloPascal (gauge).

Reference: 30.000-40.000 kPag, with fluctuations of about 2000 kPa in either direction considered normal

Fuel temperature

Temperature of the fuel entering the fuel pump. Output in degrees Celsius.

Target pump SCV current

Target electrical current of the suction control valve. The suction control valve is part of the fuel pump. It regulates the amount of fuel being fed to the plungers in the fuel pump. Output in milliamps.

Target EGR position

Position of the EGR valve as demanded by the ECU. Output in percentage.

Reference: 0-95%

EGR lift sensor volt %

Actual position of the EGR valve, as measured by the sensor on top of the valve. Fully closed at full acceleration, fully open at throttle lift-off. Anything in between during cruising speeds and idle. Having only worked on my own car so far, I assumed that this reading was fixed at around 60-70% at idle, but now that I've seen readings from other members I know otherwise.

Reference: Fully closed - Around 15%, fully open - 80-86%

EGR VSV

State of the EGR vacuum switching valve, which is used to open and close the EGR valve. Located on the side of the EGR (brown if I'm not mistaken).

VN Turbo command

Opening of the turbo variable vanes. At low rpm the vanes are partially closed for better boost at lower RPM's and they open up as the engine speed climbs. Closing vanes are indicated by an increasing percentage, and the percentage decreases with the vanes opening up.

# codes (include history)

The number of diagnostic trouble codes that are currently present

MIL ON run distance

Distance travelled since the check engine light first came on.

Running time from MIL ON

Time elapsed since the check engine light first came on

Time after DTC cleared

Time elapsed after clearing all trouble codes.

Distance from DTC cleared

Distance travelled since clearing all trouble codes

Swirl control valve VSV

State of the vacuum switching valve that opens and closes the swirl control valve, used to improve air/fuel mixing.

ON= closed swirl control valve

OFF= open siwrl control valve

A/T Oil Temp from ECT

Automatic transmission oil temperature. Output in degrees Celsius

SPD (NO)

Transmission input shaft speed. Output in rpm's

ECT Lock-up

State of the torque converter lock-up mechanism. Lock-up improves fuel economy at highway speeds.

Reference: OFF - below 80 km/h, ON - 80 km/h and above

OUT OF RANGE TROUBLESHOOTING

Troubleshooting based off these readings alone is tricky. An out of range value doesn't necessarily mean that the parts in question are stuffed. So put away your spanners for now and use the information provided as a guide only. All the information in this section is based off my own findings and input from experienced members on here.

MAF

An out of spec MAF reading might be an indicator of either a dirty MAF or blocked EGR flow among others. Usually this is accompanied by a P04XX for the blocked EGR or a P2008 fault code for the dirty MAF. Use together with MAP readings and active test within Techstream to diagnose EGR problems.

MAP

Same as out of spec MAF readings, as they usually work hand in hand. In addition, the MAP filter might be cracked or blocked. Clean, repair or replace.

Accelerator position

Problems with the accelerator pedal (dead spots or sudden power loss) are best diagnosed with the graph function within Techstream. If there are dead spots, they will show up there as sudden valleys approaching or equal to 0% when slowly pressing down or releasing the pedal.

Actual throttle position & close learning val.

Sometimes after cleaning the EGR, people forget to connect the plug of the position sensor. As it sits under the intercooler, and is hard to see afterwards this has lead to a lot of swearing.

Injection volume & feedback values

Out of spec injection volume & feedback values can mean one or more of the following:

- Blocked injector(s) (positive feedback value and low injection volume)

- Leaking injector seats, leaking valve stem seals or cracked piston (negative feedback value)

- Worn injector (negative feedback value)

Fuel pressure

Malfunctioning pressure limiter in common rail, malfunctioning pressure sensor or suction control valve. Fluctuations in actual rail pressure of 2000 kPa or 300 PSI (difference between highest and lowest readout) is considered normal. When it starts to fluctuate in the 5000 kPa (800 PSI) range it may be time to replace the suction control valve.

Target EGR position and EGR lift sensor volt %

These two values should be within 10-15% of each other during operation. If not, problems can range from malfunctioning vacuum switching or regulating valves, leaking vacuum hoses, stuck or poorly moving EGR valve stem and ECU fault. Also if the ECU detects no EGR flow, it'll throw a P0400 code and close the EGR valve. Watch these values together with the MAF & MAP readings to diagnose EGR problems. Keep in mind, if you idle the engine for more than 10 minutes, the EGR valve will also close automatically, but it won't be accompanied by a fault code. Just restart the engine or drive it around the block to restore function. If there is no EGR flow, it might be a good idea to clean the EGR cooler (or heat exchanger to some).

EGR close learn status

If this value is NG (=Not Good), it usually means the EGR valve isn't seating properly (due to sooth) or the learning cycle hasn't completed yet after ECU reset. Clean the EGR valve seat if dirty, or drive around for more than 20 minutes.

*Edited 12/12/2013 - Removed the bit about intercooler capacity. Got my math wrong

*Edited 03/01/2014 - Added boost pressure info to MAP data explanation

- Added P2008 code to MAF out of range troubleshooting

- Added pressure fluctuations due to faulty suction control valve to fuel pressure diagnostics.

Category4x4

4x4/Obd2ValuesExplained (last edited 2018-01-13 21:38:34 by PieterSmit)