Hi Guys, RB30 N/A VL Auto, Been having problems with my 4 speed 4n71b Jatco Auto Trans lately. When I start the car and drive off (Regardless of how long car has been running) when it first attempts to get into 3rd, it will hold on to 2nd until i hit about 70-80 kph or around 3-3.5k rpm. Then will only hit Overdrive after about 10 minutes of driving. After this, it generally behaves and shifts into 3rd and then overdrive fine after about 10 minutes of driving. If I turn off the ignition and turn it back on straight away, the issue starts all over again. I've check vac lines and replaced vacuum modulator on the side of the box, done fluid and filter twice, but problem is still there. My speedometer jumps around like crazy +- about 8kph going from 0 to 80kph, and then seems fine in the upper speeds. I've read this could be related to the Speedo VSS (Vehicle Speed Sensor) in the back of the dash cluster. I've ordered a new one as it's fairly cheap and will report if that was the problem, but another thing i'd like to check is the TPS Throttle Position Sensor. My TPS was replaced in the last couple years through troubleshooting a different fault in the past, but I never set it back to what it's factory resistance was, and I'm unable to find solid number to what it should be set to. This is the auto TPS with the 2 plugs, [Image in original archive] It has the sweep potentiometer style that sends signal to Auto and ECU. TL;DR Can someone please check and tell me what resistance they are getting between the centre pin and the outside pin on the grey connector of their RB30 Auto TPS plug ? Mines getting between 9k and 11k ohms, and I'm not sure where it should be set. It's different to the Manual one where it's either on or off. Cheers, ---------- Post added 06-06-19 at 04:14 ---------- So i'm not 100%, but i think these just need to be reset / calibrated, and they will 'learn' from wherever it's set and you can micro adjust idle by moving it back and forth. Not certain there's a hard setting it needs to show over the pins. Someone correct me if i'm wrong.

Hi 88, There is a self diagnosis that is meant to diagnose between VSS & TPS using the overdrive lamp, have you tried this? Does the VSS throw a code (14) on the ECM lights for engine control? With the speedo flickering badly, is the cable kinked? or does the inner cable need a bit of lube? Cheers - Leigh

Quote: Originally Posted by 88vlbt1 [View Post] Hi Guys, RB30 N/A VL Auto, Been having problems with my 4 speed 4n71b Jatco Auto Trans lately. When I start the car and drive off (Regardless of how long car has been running) when it first attempts to get into 3rd, it will hold on to 2nd until i hit about 70-80 kph or around 3-3.5k rpm. Then will only hit Overdrive after about 10 minutes of driving. After this, it generally behaves and shifts into 3rd and then overdrive fine after about 10 minutes of driving. If I turn off the ignition and turn it back on straight away, the issue starts all over again. I've check vac lines and replaced vacuum modulator on the side of the box, done fluid and filter twice, but problem is still there. My speedometer jumps around like crazy +- about 8kph going from 0 to 80kph, and then seems fine in the upper speeds. I've read this could be related to the Speedo VSS (Vehicle Speed Sensor) in the back of the dash cluster. I've ordered a new one as it's fairly cheap and will report if that was the problem, but another thing i'd like to check is the TPS Throttle Position Sensor. My TPS was replaced in the last couple years through troubleshooting a different fault in the past, but I never set it back to what it's factory resistance was, and I'm unable to find solid number to what it should be set to. This is the auto TPS with the 2 plugs, [Image in original archive] It has the sweep potentiometer style that sends signal to Auto and ECU. TL;DR Can someone please check and tell me what resistance they are getting between the centre pin and the outside pin on the grey connector of their RB30 Auto TPS plug ? Mines getting between 9k and 11k ohms, and I'm not sure where it should be set. It's different to the Manual one where it's either on or off. Cheers, ---------- Post added 06-06-19 at 04:14 ---------- So i'm not 100%, but i think these just need to be reset / calibrated, and they will 'learn' from wherever it's set and you can micro adjust idle by moving it back and forth. Not certain there's a hard setting it needs to show over the pins. Someone correct me if i'm wrong. Your speedo jumping around is a mechanical issue. The speedo is mechanically driven by a cable. All the VSS does is pick up the movement from the speedo and communicate with the auto trans control module and ecu. With the speedo jumping about, the VSS will be confused. I'd first try and sort the jumpy speedo. Either replace the cable or take it out of its outer casing, clean it and the inside of the casing, then reassemble with a light lubricant. If the speedo is still jumping then there is a mechanical issue with the speedo movement in the cluster. Get another cluster or get a gauge repair shop to fix yours.