Transmission problems with SES light

[JTrujillo86]

Before I begin, I know there has been a lot of talk about transmission issues with the Aleros. I'm reluctant to start a new thread, but I'm having differing issues than everyone else.

To the story: tonight after I left the gas station (about 3 blocks after I pulled out) my car started shifting REALLY hard. It slammed into each gear. I pulled over, shut it off, and restarted. When I shifted to reverse, it slammed there and again when I shifted from R to D. After that, first gear was the harshest, then second. I didn't feel too much going into third, but overdrive was bad as well. As I stopped at a light, I shifted to reverse to see if it would have the same issues...it did, but this time the SES light came on. The rest of the drive home, pretty much first was the worst with the others calming down a bit. When I came home and parked it, I could hear an odd roaring/hissing/ticking coming from the transmisison. NOT the engine, but the transmission.

I'm taking it in tomorrow. PLEASE help me with suggestions about what could be wrong. I'm hoping this isn't a valve body failure like my mom had in her 1999 Blazer. She had the same issues I'm describing. Honestly I can't have this happen. Tomorrow I was supposed to move back to school. I worked two jobs this summer to save up for school and to pay off my credit card, which I did. It seems like one thing after another.

- Jeremy

[BNaylor]

Doesn't sound good. Maybe a scan will show some tranny DTC error codes.

[JTrujillo86]

I took it in today. It turned out to be the IAT sensor and the wiring leading up to it. The wiring was frayed (I don't know how that happened) and the sensor itself had both excessively high and low voltage readings. When all was said and done I was $210 lighter in the wallet, but my car came back normal.

Anyone know why a temp sensor for the engine would cause the transmission to act so crazy like mine did?

- Jeremy

[BNaylor]

Originally Posted by JTrujillo86

I took it in today. It turned out to be the IAT sensor and the wiring leading up to it. The wiring was frayed (I don't know how that happened) and the sensor itself had both excessively high and low voltage readings. When all was said and done I was $210 lighter in the wallet, but my car came back normal.

Anyone know why a temp sensor for the engine would cause the transmission to act so crazy like mine did?

- Jeremy

Thats good news Jeremy. That is a symptom with a bad IAT on the 3.4L V6 for some reason. We have old posts on the IAT affecting the tranny.

[erikedu]

They absolutely smashed you on the price! The IAT sensor is only $14 and the pigtail is only $8. It only took me 30 minutes to replace the pigtail connector and 30 seconds to replace the IAT sensor.

I just came in from the cold, fixing the same problem you guys are talking about. My 3.4L V6 01 Alero was hard shifting with the Service Engine light on. The Diagnostic Trouble Code was P0113: Intake Air Temperature Circut, High Input. Hoping for the easy fix I bought and installed a new IAT sensor (AKA: Air Charge Sensor) at AutoZone for $13.99, but it didn't help anything.

The problem was the wiring leading to the sensor had broken. The IAT sensor shares the same 5V reference voltage with the Coolant Sensor and the Throttle Position Sensor. When the wire broke at the IAT Sensor, the TPS signal got messed up telling the computer to up the transmission pressure to "protect" the transmission. (Even though it felt like it was destroying the transmission)

The solution to the problem was to order a new IAT Sensor connector pigtail, GM Part #12102620/ AC Delco Part #PT307/ PICO Part # 5616. I found mine at bmotorsports.com for under $8.00 after shipping. Stagger your cuts on the pigtail wires, heat shrink both butt connectors, and re-apply some electrical tape and you'll be back to smooth shifting in no-time!