OBD II Question

[hoberock]

I have an OBD II set up that plugs into a laptop. The program can read O2 sensors, temp. sensors, speed, rpm, etc... The information I have on the OBD II data available for Disco I's says that I should be able to read the Mass Air Flow Rate information as well, however, my program says there is no data available data for MAF. Does anyone else have OBD II reader that can read sensors and does it read the MAF rate?

Thanks,
Tim

[Disco Mike]

No, I don't but I am curious why you are worried about your MAF, is the truck not running well?
Mike

[Adam in NYC USA]

You need three things here. The codereader , the engine running, and some wisdom. The MAF will read out when you have some throttle. It reads the change, the delta, of the sensor inside the MAF. The data is not raw voltage numbers nor raw data; it is processed cooked data coming from the ECU.

Put the vehicle in park and give a few jabs so you can see what the baseline looks like. Or strap in the laptop or secure it in the passenger footwell. Set the codereader program into record mode. Record the MAF, the vehicle
volacity, the mph. You then go for a cruise. Then you will see the relationships.

BTW, you can do all this easily with a Davis CarChip E/X and get some half-decent ploting to boot.

Got it now? Remember that the most important piece of equipment is you.

Adam

Adam

Adam

[hoberock]

Disco Mike, I have been fighting an idle problem for 6 months now. Last week I found some information on the GEMs operations for my '97 Disco. Gave great information on the pen outs, resistance values of various sensors, and operation theory of the system. I spent the rest of the week checking all the sesnors and found all of them (wnot including the MAF which I don't have a way to check) to work fine. I have a OBD II data logger which connects to my lap top. It is not as good as a Rovacom (which I don't have an extra $6k to purchase), but it allows me to monitor a lot of the system (like O2s and such). The program logs no data for the MAF. So that means that A) my MAF is out and is not sending data or B) the Disco OBD II does not provide MAF data. My Ford truck does provide MAF information to the program so I know that the program can log MAF data. This is way I was wondering of someone has a similar OBD II set-up and could tell me if the MAF data is or is not available via OBD II protocol for the Disco I.

Adam, my ODB II set up reads codes AND logs data (Digimoto Diagnostic with a ScanTool interface). I works fine for my fleet of other OBD II vehicles. However, Land Rovers seem to do things different sometimes. In anycase, my program gets zero output for MAF from the OBD II connection in my Rover. I get Zero regardless of gear, speed, RPM, etc. So I am wondering if the MAF data is available via the OBD II protocol on the LR or not. If it is available then my MAF probably needs replacing. As a side note, if you disconnect the MAF on my LR, it seems to idle fine and responds fine to reving the throttle (I did not try to drive it yet with it disconnected) and it does not thru an error code (which I would have expected).

Can someone help me out here?

Thanks

Has anyone been able to read the MAF output via the OBD II connection using a OBD II protocol (ie not the Rovacom or Rovacom Lite)??

[Adam in NYC USA]

I I have been able to read the MAF 'reading' from both a handheld codereader (a mid-priced Actron)and the Car Chip E/X.

You would only get an absolute positive number when you step on the gas and induce an vacuum into the intake manifold.

My suggestion is find a used working MAF and see if there is a difference. You could buy a new one but the price is steep $600. I got a used one off of eBay from a hundred and it worked fine.

http://cgi.ebay.com/LandRover-Discov...QQcmdZViewItem

Why not ask someone like carcannibals.com for a used one? If that is the problem, you can send out the original MAF for a rebuild.

[dent]

if you think it's your MAF get some electronic cleaner and give it a good squirt before going out and replacing.
if you're having idle problems, you might want to clean out your stepper motor (idle control valve). try cleaning out carbon build up first before you go and replace
sam

[Adam in NYC USA]

Cleaning your MAF would be good if you have a corroded hot-wire but it will do nothing if the hot-wire itself is open. Sometimes this happens and the effect is lousy performance ,like on a very moist day. Then replacement is the only option. He is stating he is getting no changes when he driving- that is a dead MAF.

Adam in NYC

[Rovin4life]

on the 97s on up we have had issues with the fuel pump pressure sensor going bad and causing irregular idle.

what happens is the wiring to the sensor also shares a power wire to the tps sensor and gives a misfire code as well.

you need to monitor the fuel pressure sensor voltage to see what it is doing.

if its bad you need to clean out the wiring to the pump or else replace it if it doesnt drop or change.

[hoberock]

Hi all, Thanks for the input. I cleaned the whole throttle body (inside and out including the stepper/Idle Air Control Valve). Also electrically checked the stepper coils, throttle position sensor, air temp sensor, coolant sonser, fuel pump relay, and fuel pump (which is new). No electrical issues found with those. No vacuum leaks found. Fuel pressure is around 35 psi. Cleaned the two value cover tubes entering the intake. All four O2 sensors appear to function properly. I cleaned the MAF two seperate times and saw not difference in behavior. Every once in a while it throws a P1179 code (too lean of a mix). If I clear the code, it goes away for awhile then comes back. The wiring thing that Rovin4life mentioned is something new that I have not heard. The behavior seems too consistent to be a wiring issue, however, I'll monitor this line. I am running out of things to check and I am leaning towards the MAF being the issue. Since I am not getting a MAF signal on my OBD II serial connection, I think that also makes me think it is the MAF. Thoughts?

[Rovin4life]

if you clean it and it comes back then the sensor is killed.



alot of sensors that land rover uses shares power wires to save space at the ecu, so if one goes bad then it shares a fault with the other.

same with the MAF sensors on the disco twos.