Yesterday I finished my EBL installation on my car: (88 Iroc in place of 165 ECM). Car is also supercharged with Bosch 3 Injectors.
In a quick and excited move, I forgot to set it up as a 2 bar map sensor, but car stated fine and found idle. Had a Code 33.
So, upon investigation I saw that EBL was reporting 1 Bar Map Sensor. So, I shut the car off, changed the flag to 2 bar, and started back up. Idle was a bit rougher, but was still able to find a spot and run, holding RPM between 750-800. However, code 33 persisted.

I installed the MAP sensor close to the manifold on the passenger side (close to where the factory was on MAP Cars), hose port is close to the manifold and on the same vac line as the Boot/Vac gage on the A-pillar. I used into the MAF plug green and Black/Wht for signal and ground per instructions and tapped spliced into the +5VDC supply to the tps along the valve cover on the passenger side. Connection for voltage was done with solder and confirmed continuity.

II know I have to have power, ground and proper signal since the system is working and the MAP values are changing with throttle input. Though, here is the problem, with the 2 bar I am seeing near 100kPa at idle (~19"Hg vacuum on the A-Pillar) and it start to read boost levels at about 15" of Hg. Is it possible I have a bad MAP? With 1 bar flagged it was showing 45Kpa at idle but still had a Code 33. Full disclocure, I haven't probed the plug for voltage, just assumed since The TPS is fine, the voltage supply to the MAF should be fine. I am open to whatever troubleshooting needs done. It was just late and I was done with the car for the evening.

I am using 2-Bar MAP P/N 213-1520 (Gm#12569241)

Side question so I better understand: Options are 1,2&3 Bar Maps

Is there a different scale for each of these or would the 1,2,3 Bar sensors each have the same voltage output at any given pressure and the flags are only selecting what the Voltage limits for the Malf Codes? Also, on the output side, is it high voltage for high Pressure or is the voltage scale inverse (high pressure low voltage)?

 

With 2-Bar MAP selected in the XDF, a 2-Bar MAP Sensor will indicate 100-kPa during key on in the Diagnostic screen on your WUD. Place the engine in the key on position only w/out starting the engine, switch to your Diagnostic (Sensor) screen on the WUD, and see what it is reading. If it is reading less than 100-kPa, double check the part number on your MAP sensor...

- Rob

Edit: See Mine? XDF set for 3-Bar, Diagnostic indiicating 100-kPa during key on...

 

Sure, makes sense it should see near 100Kpa without the engine running if we are near sea level. Also fair point on the part number. I have verified I have the correct box, I haven't looked at the sensor itself, yet.

 

Yeah, I just noticed you were 860' above seal level.

Upload a datalog if you have...

- Rob

 

Haven't done a data log yet. Just the first start last night and drove it at just idle around the neighborhood.

I did try a VE Learn and as I was watching it I noticed how high the Kpa was, but my A-pillar gage was showing plenty of vacuum (Relative to atmosphere). Strange thing is, my BLMs are pretty steady. I would figure being so high up on the pressure it would be trying to throw fuel in and then BLMs would start dropping to lean it out.

 

Kyle, just to be sure, when you get the chance, disconnect the vacuum line from the MAP sensor itself (not the ECM connection), then check the Diagnostic Sensor screen again w/key on engine off (indicate what the reading is). This will underline if it is a calibration issue. Yes, definitely confirm the part number as well whenever you can...

- Rob

 

Thanks, will do tonight and see what it reads.

 

Part number on the sticker attached to the MAP is correct, WUD shows 100kPa+ 12PSI Boost.

 

Don't worry about what the sticker says, that was placed on it by someone after the fact. Look on the MAP sensor itself and indicate the stamp part number just above where the ECM connector connects to it. You are looking for either; 886, 012, 539, 609 & 701 for a 2 Bar GM MAP sensor. If it is a different stamp number, indicate what it says. If the stamp number checks out though, then yes, you're going to need to probe the connector for voltage. If that checks out, then you ill need to test the MAP sensor with a hand pump w/pressure gauge to see if you have a bad one. Either that, or just borrow a 1-Bar MAP sensor from someone, install it, and see what the reading is after you flag the bin for 1 Bar MAP w/koeo (key on engine off)...

- Rob

 

I looked at the sensor and it was not stamped. While it was in an AC Delco box, I think I saw "Made in China" and A B C on the plug. I will look again to confirm. I found the below information yesterday while looking around.



One thing for sure, there is no GM on my Map.

Another fun part... since my car was Supercharged when I got it, the PO had to extend the MAF plug to put the MAF out where the Charcoal canister was. Lucky for me this meant I had enough plug length to run under the plenum and get close to where the factory location for the MAP is on later cars. I need to probe the connector and make sure something in the color combination hasn't caused me to use the wrong wire. it looks like it is getting close to 5V to the ECM based off the chart.

 

I was just talking to RBob about this recently. Sometimes, depending on the manufacturer and brand, the wires might need to be "inverted" for whatever reasoning due to assembly. So yes, be sure that the connector keying matches the sensor pinouts...

- Rob

 

I thought I had follower it per Rbob's instruction and the ABC is on the MAP. I was thinking I might have crossed a wire because the PO did use wires close in color, but different, but that would be strange given its a 3 pin connector. 5V to it, confirmed that. For it to work it would have to be grounded, and there is only one other wire, it is connected to the ECM as a signal. I don't think there is a way to send a straight 5V to the ECM with this connector, but based off the chart, that is what seems the ECM is seeing.

Would there be any other way for it to work? Power/Ground swapped maybe,but I am thinking the signal wire has to be right for the ECM to be getting feedback.

 

Pin C to Pin A KOEO, 4.5V
Pin A to Pin C KOEO, -4.5V

Voltage may be a tad low because I have a booster pump that comes on

ECM is obviously getting a signal.?

 

After doing some more playing, I think I have something out of place. With the MAP disconnected, the car idles like it has a big cam in it, but the MAP shows 82KPa, but is responsive to throttle change... again, MAP not connected and Vac Line capped.

Idle with no MAP Connected



So, I guess I went wrong on re-pinning?

What should I be looking for?

 

The MAP wiring is likely incorrect. Maybe signal and ground are reversed. The reference voltage from the ECM should be dead on at 5.0V. Check it at the MAP connector with it disconnected from the MAP sensor.

If you have a 1-bar MAP plug it in and see what happens.

BobR.

 

Fair enough, I am pretty sure I did that by taking a voltage reading from C to A getting a positive voltage and the same reading but negative voltage A to C.

Also, the ECM appears to be getting variable voltage while the car idles with the MAP unplugged and it responds to throttle input.

 

With an active code 33 (MAP high), the ECM goes into n-alpha mode and creates a MAP value via RPM and TPS%. This is why you should always use the diagnostic display of the WUD for troubleshooting. It shows the raw sensor data, whereas the main WUD display shows what the ECM is using, even if it is a default value.

RBob.

 

Thanks, yup just learning the system. This is why I chose EBL for the support. This gives me something else to look at then and I will tonight.

So why would it be picking a value so high though?

 

It isn't calibrated for the 2-bar MAP. It would be about half that value (of the 82 KPa) if the 2-bar MAP flag wasn't set.

Halve the values in this table: NAlpha - MAP KPa vs RPM & TPS (2bar)

Can highlight the whole table and multiply by .5

RBob.

 

Hey, thanks... I found the problem. When the MAF plug was extended by the PO, they didn't have all the colors GM did when they made the wiring harness. both the Black and Black/White were extended with a black wire. I had picked the wrong one.

All is well now. Time to get tuning.

I did learn a lot about MAP sensors and some about the tuning from dealing with this. Probably will worth it in the long run.I adjusted the nAlpha table and flashed a tune before I found the problem. It did run better.