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Discussion Starter #1
<<<Shoutout to Forscan providing amazing diagnostic insight, what a great program. Below is a nice example of some diagnostics and help request>>>

2006 Mazda3 BK 2.3L 5AT.

So I have driven around for 18months with intermittent TCM issue, now I discovered the DTC:

P0715 - Input/Turbine Speed Sensor (TSS) Circuit
Fault Description: (From Mazda service manual) "no TSS signal received for 0.7sec AND Speed > 42km/hr"

So recorded some TCM PID's in Forscan. Start engine, accelerate, observe fault as soon as reach 42 km/h for 0.7 seconds.

[TSS, 1/min] reads zero speed from ignition until the fault occurs [DTCCNT = 1]. After fault occurs, the TSS immediately provides good data. TCM performance is perfect from then on, and no problems. Next cold start, same cycle.

I’ve read the other threads on P0715 and note TSS replacement or TCM. I suspect an electrical gremlin.

Anyone suggestions for root-cause?

(Note TCM PID's shown):
[Turbine Speed Sensor (TSS), Throttle Position (THOP), Transmission Fluid Temperature (TFT) , Intermediate Speed Sensor (ISS), Output Speed Sensor (OSS), Freeze-Frame Data (FFD), Vehicle Speed Sensor (VSS.OBDII), DTC Count (DTCCNT), TCM Voltage (...R.OBDII), Engine RPM (....BDII)]

105533
 

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<<<Shoutout to Forscan providing amazing diagnostic insight, what a great program. Below is a nice example of some diagnostics and help request>>>

2006 Mazda3 BK 2.3L 5AT.

So I have driven around for 18months with intermittent TCM issue, now I discovered the DTC:

P0715 - Input/Turbine Speed Sensor (TSS) Circuit
Fault Description: (From Mazda service manual) "no TSS signal received for 0.7sec AND Speed > 42km/hr"

So recorded some TCM PID's in Forscan. Start engine, accelerate, observe fault as soon as reach 42 km/h for 0.7 seconds.

[TSS, 1/min] reads zero speed from ignition until the fault occurs [DTCCNT = 1]. After fault occurs, the TSS immediately provides good data. TCM performance is perfect from then on, and no problems. Next cold start, same cycle.

I’ve read the other threads on P0715 and note TSS replacement or TCM. I suspect an electrical gremlin.

Anyone suggestions for root-cause?

(Note TCM PID's shown):
[Turbine Speed Sensor (TSS), Throttle Position (THOP), Transmission Fluid Temperature (TFT) , Intermediate Speed Sensor (ISS), Output Speed Sensor (OSS), Freeze-Frame Data (FFD), Vehicle Speed Sensor (VSS.OBDII), DTC Count (DTCCNT), TCM Voltage (...R.OBDII), Engine RPM (....BDII)]

View attachment 105533
Did you ever find the issue? My 2006 Mazda 5 2.3L seems to have this same exact issue.
 

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Discussion Starter #3
I have dug into the engine bay, electrical connection between TSS / TCM looks ok with multimeter, harness, connectors and pins are dirty and old but ok. I’m still suspicious of them as the two TSS wires which carry the pulse are susceptible to noise and should be shielded with a grounded sheath (not sure how to check this). Checked resistance of the sensor resistance is in spec. Removed the sensor from transmission housing and it looked clean but I wiped it down to confirm no iron filing build up on it.

Reassembled and drive around recording data again. Thought I’d got rid of the problem as sensor was giving good data from startup, alas the fault did still occur at one point in the drive but the sensor data was way cleaner and the fault didn’t happen straight away as it used to.

So I thought I may as well buy a new sensor and try that - OEM sensor is $120 but I got a cheap one for like $30 on eBay from China.

Because I am in Covid lockdown in Melbourne Australia, I’ve not needed the car for months, I have not actually bothered to try that new sensor out, or to go for another drive to confirm the fault behaviour. The cars been in my yard since this first post, waiting for me to test it again before trying the new sensor. Maybe I am enjoying the hope that it will work and am procrastinating that test as it will collapse my hope to the reality of it either working or not!

I will come back here when I try the next step and update.
 

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Discussion Starter #4
UPDATE:
I replaced the Turbine Speed Sensor (aka pulse generator) and problem has gone away. Also wrapped some electrical tape around each of the two wires adjacent to the sensor connector where they were not sheathed by the black housing adjacent to the connector back side.

Early days with only a few test drives, so I’m still nervous it will come back. But the fault was there EVERY time I drove for the last 2 years!

Image of the old sensor and part number of the replacement. Although the old sensor read 300ohms (in spec) the only apparent flaw is the metal bracket is quite loosely attached to the plastic sensor housing.
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