Hyundai Forums banner
1 - 3 of 3 Posts

2 Posts
Discussion Starter · #1 ·
Both generation years of hyundai sonota and kia optimas are notorious for bad input and output speed sensors. i was trying to replace the input and output speed sensors myself and I wired one or two of them wrong. I think i wired the output wrong if i remember correctly. (center wire was correct the other 2 were wrong) immidiately after i did that while trying to test drive it, i lost my odometer lights PRND lights in dash and on the gear shifter and the RPMs would show but the MPH would stay at zero regaurdless of speed.
It shifts hard with a delay from Park to Reverse, from Reverse to Neutral and from Neutral to Drive. any way i shift it it laggs and jerks hard (an issue i never had before)

while it was throwing the original codes it just got stuck in 2nd gear (limp mode)
i had replaced the sensors and it ran fine for a day then got stuck again, replaced it twice ran fine for 10 minutes got stuck again. ( taking sensors from junkyard)

Original codes were P1529 mil/tech (TCM Request For MIL On, Check for trouble codes in TCM, TSB 1-40-005 (3/01) contains information about this code.
P0715 input speed sensor [short circuit/open switch, No input speed sensor output pulse detected for >1 second at vehicle speed of >30km/h]
P720 output speed sensor [short circuit/open circuit At vehicle speed of >30km/h, output speed sensor <50% of vehicle speed sensor output for >1 second.

after i wired the sensor(s) wrong
i think i wired the output wrong.
i tried to replace the TCM and went thru about 5 from the same gen/year till i found one of the same color (original blue KIEFKO90909301821A.
THC159-F2. HX. 138426F 0772
other 4 were red .

the new TCUs didnt fix the problem but did throw.
P1602 Serial communication problem with TCU. TCM has failed. CAN network open or shorted to ground. CAN network shorted to VREF power (B+)
the sensor i fried has a ground, a 12 volt power input and a 5V REFrence . if anything most likely out of all these codes i probably did.
CAN network shorted to VREF power (B+)

i learned that VREF=volt reference=output signal from sensor and that B+ is the 12v supply that is hot at all times.

I'm going to try to test(for continuity)/replace the Transmission range switch [transaxle range switch] [A/T control relay, Solenoid Valve checks] i have both the service manual and electrical troubleshooting diagrams but i'm still learning how to read the elec. diags.

hooked a scanner up and while in park it said,
Air flor rate from MAF 16969.42 lb/hr
Voltage for MAF/\^^ 0.9v
Vehicle speed 118.68mph
RPMs 48130

garbage in garbage out:cry:

I could junk this car for $1,500 but i'd much rather keep it the interior is nice it rides like new no trans issue other than the one i may have caused by my ecludian wiring.

☆☆☆KEY () emphasis [] quouting from service manual☆☆☆

If anybody can help me or give me advice that results in me fixing it i'd be willing to pay

other facts i replaced the timing belt, cam sensor, throttle position sensor, and crank sensor with no issues

please help thank you.

Drives : Nissan NV200 Flies : Rans S6ES
17,991 Posts
the new TCUs didnt fix the problem but did throw P1602 Serial communication problem with TCU.
Put the original TCM pack on. And don't replace any other parts. Your just adding more & more variables into the mix. Diagnosis is about trying to remove as many variables as possible, not adding new ones.

Did you fix the wiring on the sensor you got wrong?
Disconnect the input/output sensors, clear the trouble codes, and rescan it. What codes do you have now?

If I helped you fix it, why not...

Your support is greatly appreciated

2 Posts
Discussion Starter · #3 ·
i did put the original back before i sent it to a shop. Just got it back yesterday. I haven't replaced the range switch yet. I'll recheck my wiring for the input and output sensors and check the range sensor for continuity.
after i mis-wired the outpit sensor all it put out was P1529 (original tcu) serial communication error with tcu.
1 - 3 of 3 Posts