MAFT Pro and TCCS Diagnostic Codes
Applicable to ALL 7M Series Toyota installations.

When installing the MAFT Pro certain functions formerly handled by the TCCS (aka ECU) are now handled by the MAFT Pro and the ECU is fed air flow data that's already been adjusted for these conditions. In this case I am specifically referring to the air density changes due to temperature changes and altitude. The fact that the MAFT Pro will be handling these calculations isn't an issue in itself so long as the TCCS is fed a valid static (not changing) signal. The problem is further complicated if the TCCS doesn't receive these signals within a certain period after powering up. There are two ways of handing this.

The MAFT Pro has 2 voltage outputs** which may be used to supply the TCCS with data to satisfy the aforementioned requirements. Most of the write ups that I have seen tell the installer to use these in order to supply the previously mentioned signals. These signals are supplied to the THA and HAC (7M-GTE) contacts on the ECU.

**In the case of the 7M-GE (non-turbo) one of these outputs is used to supply the air flow data, so there remains only one programmable voltage output at your disposal.

However, there are two other reasons to use an alternative solution to provide these signals. By using something known as a resistor network you can supply a preset voltage to each input where it is needed, keep the MAFT Pro's outputs available to use with other features (such as the Enhanced TPS feature found in software version 5.0 and newer), AND you can avoid error codes you would otherwise set if the ECU powers up before the MAFT Pro does.

A resistor network uses two or more resistors connected in parallel, serial or combination of the two. By using two resistors between VC and E2 you can create a supply of 2.5v for THA.

VC supplies 5v, this is what feeds Vin in the above diagram. E2 is the sensor ground. If R1 and R2 (resistors) are of the same value the result at Vout would be one half of that supplied at Vin.

----------7M-GTE Specific---------
For you turbo guys you want to put a 2.2K resistor between THA and E2. This will give the ECU an intake air temp of about 68ºF. This may be a little aggressive for those of you in hotter climates though, so keep thin in mind. If you want to tell the ECU something a little warmer you could use a resistor between 1.2K and 1.5K. You can reference the chart HERE if you want to see what the ECU is set to per an approximate amount of resistance.

Then you would use a 1.2K resistor for R1 and a 2.7K resistor for R2 to supply HAC with a signal voltage of 3.46v. (The values shown in the diagram below are perfectly acceptable as well. They provide a signal of 3.41v.)

Diagram courtesy of Bob Bailey.

--------End 7M-GTE Specific--------

----------7M-GE Specific---------
On the 7M-GE for THA you would use one 1.2K resistor for R1 and another 1.2K resistor for R2, this will supply your THA signal of 2.5v.

You don't have a HAC sensor, so that's the end of the resistor fun... keep reading though, you're not in the clear. The next thing you need to do is to set up the MAFT Pro so it powers up BEFORE the TCCS (ECU). We'll do this with a relay and three diodes.

--------End 7M-GE Specific--------

The great thing about this method is that the ECU receives the required signals as soon as it starts (since the signals' voltage is supplied by the TCCS)... so, no more codes... well, you're still likely to get an air flow error code, so continue reading.

Click here to continue: Pre-powering the MAFT Pro from the Acc. circuit