Sharing TPS signal with oem ecu

Ask questions about DIY board assembly issues, fault finding and testing. (Covers all Megasquirt versions and board.)

Moderators: jsmcortina, muythaibxr

Sharing TPS signal with oem ecu

Postby PauliusB2 » Fri Oct 06, 2017 10:58 am

Hello. I'm installing ms2 on my friends Lexus GS300 (2JZGE) inline with OEM ecu (to control electronic throttle body, save cruise control, traction control and automatic transmission control) and have a issue with tps. When I splice in for tps signal, car brings up an traction control warning light on the dash (because of tps problem).
MS reads tps signal with no problem, car starts and runs on MS and doesn't bring up any warning light when MS is disconnected and it runs on OEM ecu.

Do anyone know how MS interferes tps signal or what could be done to fool OEM ecu, so it could read tps without fault warning?
I forgot to measure tps output voltage with and without MS connected. Maybe just parallel or series resistor would help if MS brings up or down tps output voltage just by reading it? I can't work on the car at this moment, my friend lives in other city. Just gathering ideas for the moment.

The goal is to control fuel and spark with ms and leave electronic throttle, cruise cintrol, transmission control and other stuff to OEM ecu.

Sorry for my bad English, I hope You understood my problem.
PauliusB2
MS/Extra Newbie
 
Posts: 3
Joined: Mon Jul 03, 2017 3:03 am
Location: Lithuania

Re: Sharing TPS signal with oem ecu

Postby billr » Fri Oct 06, 2017 1:22 pm

The MS TPS input should be a quite low load, but the OEM system may be very fussy because it is DBW. I assume you have little info on the OEM TPS circuit. I would start by connecting dummy resistors between the TPS signal and ground, with the MS disconnected. By using different resistors, try to determine what kind of load the OEM ECU can tolerate before reporting a problem.
billr
Super MS/Extra'er
 
Posts: 5015
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Sharing TPS signal with oem ecu

Postby jamies » Sat Oct 07, 2017 2:38 am

are you splicing just the tps wire or are you splicing VREF and GND too?
jamies
Experienced MS/Extra'er
 
Posts: 342
Joined: Tue Apr 07, 2009 12:22 am

Re: Sharing TPS signal with oem ecu

Postby PauliusB2 » Sat Oct 07, 2017 2:55 am

Just TPS wire. Why should i need to splice vref and gnd?
PauliusB2
MS/Extra Newbie
 
Posts: 3
Joined: Mon Jul 03, 2017 3:03 am
Location: Lithuania

Re: Sharing TPS signal with oem ecu

Postby jamies » Sat Oct 07, 2017 3:57 am

you may need to link ms signal ground with oem tps ground as sometimes oem use floating grounds. the ms shouldnt load the TPS signal that much that it will throw the oem ecu out of whack.
if it was a self built ms2 might be worth checking resistance between tps wire and signal ground incase some components are not correct. you could also try a 4.7k resistor in series with the tps wire
jamies
Experienced MS/Extra'er
 
Posts: 342
Joined: Tue Apr 07, 2009 12:22 am

Re: Sharing TPS signal with oem ecu

Postby PauliusB2 » Sun Oct 08, 2017 4:10 pm

Thank You for suggestions. I will try them and report the results.
PauliusB2
MS/Extra Newbie
 
Posts: 3
Joined: Mon Jul 03, 2017 3:03 am
Location: Lithuania


Return to Board assembly and testing

Who is online

Users browsing this forum: No registered users and 2 guests