Details: LS2/T56 swap in 67 camaro. E38 with new stand alone harness. Bone stock LS2 with 230/232 112 cam. Been chasing this for a few months, and I have run down the checklist of things that could trigger this code- wiring, vacuum leak, ECM pin locations- everything checks out. At idle, map output is 2.2v, and I believ it should be around .5v The car runs and drives perfect, but is a bitch to get started. When the map code is cleared, starts right up. Code comes back immediately. I have done 10 LS swaps, and never had this issue. Same tuner, same harness builder. Tuner says map looks to be functioning normally. With nothing left to check, im looking toward the tune. What part of the tune do I have the tuner start with?

 

Conditions for Running the DTC

P0108

DTCs P1516, P2101, P2125, P2135, P2138, P2176 are not set.
The engine has been running for a period of time that is determined by the start-up engine coolant temperature (ECT). The time ranges from 8 seconds at less than -30°C (-22°F) to 3 seconds at more than 30°C (86°F) .
The throttle angle is less than 1 percent when the engine speed is less than 1,200 RPM . OR
The throttle angle is less than 20 percent when the engine speed is more than 1,200 RPM .
This DTC runs continuously within the enabling conditions.

Conditions for Setting the DTC

P0108

The ECM detects that the MAP sensor voltage is more than 4.9 volts for more than 4 seconds

Circuit/System Testing

Important: All electrical components and accessories must be turned OFF and allowed to power down.

Ignition OFF, disconnect the MAP harness connector at the MAP sensor.
Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit and ground.

¤ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit and ground.

¤ If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
¤ If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

Verify the scan tool MAP Sensor parameter is less than 12 kPa .

¤ If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify the scan tool MAP Sensor parameter is greater than 103 kPa .

¤ If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

If all circuits test normal, test or replace the MAP sensor.

 

I have done most of that, although I did not ohm it out. My scan tool does not report live data, but I can get that covered. This diagnostic is a bit more in depth than the one I used, thank you for posting it.

 

All of the above checks out, other than the map's output voltage at idle is higher than it should be. Out of desperation I changed intake gaskets, even though it showed no signs of a vacuum leak. Surprisingly the code did not return after a short drive. After a 30 min trip, it had come back on. My LS3 has 12" vacuum, and this LS2 has 11". Cams are very similar. Any other ideas?

 

In kPa units, not " of vacuum, what does the MAP read with KOEO? What does it read at idle? What does it read at part throttle cruise? What does it read at WOT?

 

I have no way to read the data. I'm bringing it to a friend's shop this afternoon to scan it w tech 2.

 

It's 2017. OBD2 has been around for over 20 years now. If you've really done 10 LS swaps then it's past time to put a graphical data logging scanner in your tool box. For $500 you can have HP Tuners and have the ability to look at the PCM calibration and have a recording data logging scanner. I'm amazed all the time with people who want help diagnosing modern EFI problems without the ability to look at live sensor data in a meaningful way.

 

Agreed, I plan to buy the HP tuners. Should have done so years ago. Just bought a new laptop before xmas, solely for HP tuners. I have a decent code reader with freeze frame data, but it just crapped out. My spare time has been consumed with this map issue for months, and I could have the car sold as soon as its resolved.

 

I have this same P0108 issue with a TBSS LS2, vette intake, LS3 throttle body. Hoping that this info will help me diagnose the problem soon.... Clearing the code without knowing where it's coming from is driving me crazy!

 

I now have HP tuners pro, hope to have it loaded this weekend. I may have pinned the code issue to the pcv system. I may have a problem with the pcv system in valley cover. I found adding an inline pcv vave to that hose keeps the code from triggering. I'm not quite sure if its the valley cover, or masking a different issue. However, I'm still having a hard time starting the car. Still runs/drives perfect. As soon as I can figure out HP tuners, I'm going to post the tune up.