The always frightening electrical problems

cre · 01-26-2012, 12:33 AM

I already answered that. To clarify: Some will show up at the ECU power up diagnostic; Some will appear when you run the car for a couple minutes (just idling will do); Some require the engine to be up to normal operating temp and running; And some require you to drive the vehicle to give it a chance to sample data at various load levels.

supraheelfan · 02-13-2012, 09:53 PM

I have a question: A mechanic I just recently met said since I have a used JDM engine and the original ECU wiring harness from the old 7mgte, that I need to "upgrade" by getting some new sensors so the ECU can read the signals it needs to operate the engine. Is any of this true? He wouldn't clarify which sensors he was talking about and he said there is about 3 sensor that needed to be upgraded..

cre · 02-13-2012, 10:03 PM

The ONLY sensor which isn't cross compatible is the oil pressure sensor. If it's a California car (originally sold in Cali) the ECU will also be expecting signal from a sensor in the EGR cooler which other MKIIIs don't have; As you don't have an error code for that sensor I assume that to not be a Cali vehicle or the swap was more complete.

Does your oil pressure gauge work?

How does he know it's JDM? It's not written anywhere and aside from the oil pressure sender and the way the coolant is routed there are no other differences.

cre · 02-13-2012, 10:51 PM

I suppose it is worth mentioning that there were a number of changes made to the electrical system throughout the '89 model year. Pretty much all of the components are cross compatible but most have different plugs, the wire harness changed, the external HAC sensor was built into the ECU, the ECUs are different (many different models actually but the only significant difference it the redline depending on wether the engine has a 6M or 7M crank). The AFM and TPS connectors are the same as are all of the temp sensors and the oil pressure sender, the CPS is different and you wouldn't be able to plug it in and the wrong TPS will plug in but the interface tabe will be clocked 90? differently than the tabs on the throttlebody. The significant differences in ECU are highlighted by the harness connector colors.... Basically, if plugs and connectors are yellow it'll work and if they're both grey it'll work.

Again, it doesn't sound like any of this is the case with your vehicle.

supraheelfan · 02-14-2012, 07:17 PM

Actually my oil pressure gauge did not work for a long time until recently my dad and me installed a Prosport oil pressure gauge, but before that it didn't work at all. Still no error codes and the only lead is this new mechanic however I don't know if he is right or just trying to get more work ya know.

This is off topic, however my dad and I have been in an on-going debate about the oil pressure sender; Does the Prosport sender need an adapter to work? The reason I ask is because my dad hooked the sender up (somehow) and now the gauge reading is way off. Just wondering cause the sender was really hard to get into the block and from the search on the internet the sender needed an adapter to go from NPT to BPT or something like that. Any knowledge about this is appreciated.

cre · 02-14-2012, 07:53 PM

The oil pressure port is a similar standard to BSP it's JIS actually. BUT there may be a bigger issue... the ECU requires an oil pressure signal from the stock sender. There is a port about 6" to 8" forward of the oil pressure sender's port you may use for your aftermarket sender with less worry about distorting the threads.

EDIT: Scratch that... why don't you check if any sensors are unplugged because the harness won't connect and look up the part numbers. If you look in the TEWD you'll find diagrams of what the connectors are supposed to look like for each sensor and in the TSRM you'll find how to measure each one and what the readings should be. A quick glance in Toyota's Electronic Parts Catalog doesn't show any as being specific to the US but the European market did have some which were different than elsewhere... I didn't check if those applications were for Supras though, could have been Cressidas or 4Runners, etc. The year of the sensor is the only issue I've ever had and heard of from others.

Start here:
http://www.cygnusx1.net/Supra/Librar...spx?F=8401&P=1
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/

supraheelfan · 02-14-2012, 10:58 PM

Uh oh! The TSRM is not loading for me is it down?

01-26-2012, 12:33 AM	#1
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	I already answered that. To clarify: Some will show up at the ECU power up diagnostic; Some will appear when you run the car for a couple minutes (just idling will do); Some require the engine to be up to normal operating temp and running; And some require you to drive the vehicle to give it a chance to sample data at various load levels. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

02-13-2012, 10:03 PM	#3
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	The ONLY sensor which isn't cross compatible is the oil pressure sensor. If it's a California car (originally sold in Cali) the ECU will also be expecting signal from a sensor in the EGR cooler which other MKIIIs don't have; As you don't have an error code for that sensor I assume that to not be a Cali vehicle or the swap was more complete. Does your oil pressure gauge work? How does he know it's JDM? It's not written anywhere and aside from the oil pressure sender and the way the coolant is routed there are no other differences. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

02-13-2012, 10:51 PM	#4
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	I suppose it is worth mentioning that there were a number of changes made to the electrical system throughout the '89 model year. Pretty much all of the components are cross compatible but most have different plugs, the wire harness changed, the external HAC sensor was built into the ECU, the ECUs are different (many different models actually but the only significant difference it the redline depending on wether the engine has a 6M or 7M crank). The AFM and TPS connectors are the same as are all of the temp sensors and the oil pressure sender, the CPS is different and you wouldn't be able to plug it in and the wrong TPS will plug in but the interface tabe will be clocked 90? differently than the tabs on the throttlebody. The significant differences in ECU are highlighted by the harness connector colors.... Basically, if plugs and connectors are yellow it'll work and if they're both grey it'll work. Again, it doesn't sound like any of this is the case with your vehicle. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

02-14-2012, 07:17 PM	#5
supraheelfan 3" Exhaust Join Date: Feb 2011 Location: Wilmington, NC Posts: 178	Actually my oil pressure gauge did not work for a long time until recently my dad and me installed a Prosport oil pressure gauge, but before that it didn't work at all. Still no error codes and the only lead is this new mechanic however I don't know if he is right or just trying to get more work ya know. This is off topic, however my dad and I have been in an on-going debate about the oil pressure sender; Does the Prosport sender need an adapter to work? The reason I ask is because my dad hooked the sender up (somehow) and now the gauge reading is way off. Just wondering cause the sender was really hard to get into the block and from the search on the internet the sender needed an adapter to go from NPT to BPT or something like that. Any knowledge about this is appreciated. Last edited by supraheelfan; 02-14-2012 at 07:38 PM.

02-14-2012, 07:53 PM	#6
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	The oil pressure port is a similar standard to BSP it's JIS actually. BUT there may be a bigger issue... the ECU requires an oil pressure signal from the stock sender. There is a port about 6" to 8" forward of the oil pressure sender's port you may use for your aftermarket sender with less worry about distorting the threads. EDIT: Scratch that... why don't you check if any sensors are unplugged because the harness won't connect and look up the part numbers. If you look in the TEWD you'll find diagrams of what the connectors are supposed to look like for each sensor and in the TSRM you'll find how to measure each one and what the readings should be. A quick glance in Toyota's Electronic Parts Catalog doesn't show any as being specific to the US but the European market did have some which were different than elsewhere... I didn't check if those applications were for Supras though, could have been Cressidas or 4Runners, etc. The year of the sensor is the only issue I've ever had and heard of from others. Start here: http://www.cygnusx1.net/Supra/Librar...spx?F=8401&P=1 http://www.cygnusx1.net/Supra/Library/TSRM/MK3/ __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar ---> Last edited by cre; 02-14-2012 at 08:37 PM.

02-13-2012, 09:53 PM	#2
supraheelfan 3" Exhaust Join Date: Feb 2011 Location: Wilmington, NC Posts: 178	I have a question: A mechanic I just recently met said since I have a used JDM engine and the original ECU wiring harness from the old 7mgte, that I need to "upgrade" by getting some new sensors so the ECU can read the signals it needs to operate the engine. Is any of this true? He wouldn't clarify which sensors he was talking about and he said there is about 3 sensor that needed to be upgraded..

02-14-2012, 10:58 PM	#7
supraheelfan 3" Exhaust Join Date: Feb 2011 Location: Wilmington, NC Posts: 178	Uh oh! The TSRM is not loading for me is it down?

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