TPS problem 1986 Pickup

Tiny
CABLE82
  • MEMBER
  • 1986 TOYOTA PICKUP
I have a technical question with my March of 1986 Toyota Pickup 4x4 Turbo pickup. I am only getting about 9 miles to the gallon out of it which I know I should be getting more. The motor is recently rebuilt along with a new turbo. My truck keeps throwing code 7 which is the throttle position sensor. I have replaced it with 6 different ones for that truck aftermarket and OEM. The problem I am having is that at the computer or at the sensor everything checks out except that I have battery voltage at IDL / E2 test and at IDL / E1 when the throttle body is opened. According to all the test sheets I have for diagnosing the throttle position sensor it should be between 4 to 6 volts. Also on IDL / E1 it says I should have 0 Ohms with the throttle valve shut but I have 844 ohms of resistance. Everything on the throttle position sensor checks out within specs if disconeted or connected, either at the computer plug in or at the sensor except for what I just described. If I clear the code, start the truck open the throttle, turn off the truck, check the code, it is instantly back. Also from time to time I will have code 6 witch is the ignitor code, but that is way less frequent and hasn’t showed up in about three months. My question is where the hell would it get battery voltage from when the throttle is opened? Is it at the ECU itself? Is there a resistor in the ECU that possibley is burned out or is the TPS intergrated into another sensor that I don’t know about? If it was a resistor in the ECU shouldn’t I get no voltage period if it is burned out?

Here are the test results

TCCS Voltage & Resistance Specs
Terminals Position of Procedure Condition Normal Volt reading Normal Resistance What I have
conector at ECU Or Ohms readings Ohms
Bat/E1 & Connected N/A N/A 10-14 volts N/A OK
Batt/E1

+B1/E1 &
+B/E1 Connected Ign On N/A 10-14 volts N/A OK

IDL/E1 Connected Ign On Throttle 4-6 volts N/A 11.66 volts
Valve Open

IDL/E1 Disconnected Ign Off Throttle Infinity N/A OK
Valve Closed

IDL/E1 Disconnected Ign Off Throttle 0 Ohm 0 844Ohm
Valve Closed

IDL/E2 Connected Ign On Throttle 4-6 volts N/A 11.66 volts
Valve Open
Do you
have the same problem?
Yes
No
Sunday, January 14th, 2007 AT 10:35 PM

4 Replies

Tiny
CARUNDELL
  • MEMBER
Hey cable, let me check a schematic and I'll get back to ya

Chris
Was this
answer
helpful?
Yes
No
Monday, January 15th, 2007 AT 5:20 AM
Tiny
CARUNDELL
  • MEMBER
Hey,
I emailed you a wiring diagram. After a review of the troubleshooting guide. (Mine was similar to yours) it looks like 3 possibilities left

1. Circuit/harness break
2. Bad ground to pcm/tps (i would go there first!)
3. Faulty pcm

back then they really lacked in diagnostic trouble shooting guides, but I would verify every inch of that harness and grounds before I would condemn the pcm. Let me know!

Chris
Was this
answer
helpful?
Yes
No
Monday, January 15th, 2007 AT 5:53 AM
Tiny
CABLE82
  • MEMBER
I didn't mention I did check all the grounds and they were fine to. Here is what confuses me, if there is a break in the wiring somewhere, shound't I get no voltage instead of battery voltage? Unless the wire is broke into another wire that carries battery voltage. Here is the strange thing. . My father also has an 86 non turbo 2wd EFI truck, same codes, except he gets 32 miles to the gallon, granted he has changed some things around to get better milage.
Was this
answer
helpful?
Yes
No
Monday, January 15th, 2007 AT 9:53 PM
Tiny
CARUNDELL
  • MEMBER
Hey cable,
Interesting (about your dads truck) there may be a bit of a trend goin' on here. Will do a bit more research and get back to ya

Chris
Was this
answer
helpful?
Yes
No
Wednesday, January 17th, 2007 AT 5:35 AM

Please login or register to post a reply.

Recommended Guides