Hello. I recently purchased a 2010 CX7 with a 2.5L automatic 5 speed.

I have three error codes, two I know are powertrain/transmission related. The car has a problem in 2nd gear and reverse, and the AT light sometimes goes on or off, and it will not stay in MT. If I start the car and put it into M1 itll shift from M1 to M3 (skip 2) and then switch back to AT in a couple minutes. I think it might be a speed/sensor shift position solenoid/sensor, I have 3 of these types of parts but haven't installed them yet.

1) P0732.00-6C gear 2 Incorrect Ratio
2) P0734:00-6C gear 4 incorrect ratio

The next one is the one that is stumping me:
3) U0073:00-28 Controll Module Communication Bus off

What could this possibly relate to?

Thank you.

Vehicle info: 2010 CX7 2.5L
Mileage: 110000 Miles
VIN: JM3ER2W50A0310779
Transmission: 5-SPEED AUTO OD TRAN
Trim: SV
Engine: 2.5L DOHC I-4 ENGINE
Int / Ext Color: BLACK / LIQUID SILVER METALLIC

 

DTC P0732:00

Gear 2 incorrect ratio
DETECTION CONDITION
• The TCM detects that revolution ratio of the input revolution to output revolution in 2GR is more than 2.157 or less than 1.249 three times.
Diagnostic support note
• The MIL does not illuminate.
• The AT warning light illuminates if the TCM detects the above malfunction condition during the first drive cycle.
• PENDING CODE is not available.
• FREEZE FRAME DATA is not available.
• The DTC is stored in the TCM memory.

POSSIBLE CAUSE
• Deteriorated ATF
• ATF level low
• Solenoid valve malfunction― Pressure control solenoid A
― Shift solenoid A
― Shift solenoid B
― Shift solenoid C• Line pressure malfunction
• Stall speed malfunction
• Forward clutch slipping
• 2-4 brake band slipping
• Primary control valve body malfunction
• TCM malfunction
======================================DTC P0734:00

Gear 4 incorrect ratio
DETECTION CONDITION
• The TCM detects that revolution ratio of the input revolution to output revolution is more than 1.249 or less than 0.6 when the following conditions are met.― 4GR
― Vehicle speed: more than 35 km/h {22 mph}• The TCM detects that revolution ratio of the input revolution to output revolution is between 0.91—1.09 when the following conditions are met.― 4GR
― Vehicle speed: more than 46 km/h {29 mph}
― TCC operation: OffDiagnostic support note
• The MIL does not illuminate.
• The AT warning light illuminates if the TCM detects the above malfunction condition during the first drive cycle.
• PENDING CODE is not available.
• FREEZE FRAME DATA is not available.
• The DTC is stored in the TCM memory.

POSSIBLE CAUSE
• Deteriorated ATF
• ATF level low
• Solenoid valve malfunction― Pressure control solenoid A
― Shift solenoid A
― Shift solenoid B
― Shift solenoid C• Line pressure malfunction
• Stall speed malfunction
• Forward clutch slipping
• 2-4 brake band slipping
• 3-4 clutch slipping
• Primary control valve body malfunction
• TCM malfunction
==================================
U0073:00
Do you have the ability with your scan tool to carry out a network test? I would be inclined to concentrate on the the two "P" codes 1st.

 

No Check engine light has ever come on.

AT lights flash during RPM changes while driving and will kick out of Manual and not go back unless I turn the ignition off and then back on. Then manual works for a couple minutes and AT flashes and manual turns off and AT flashes.

I did buy a solenoid and two or three other sensors for the transmission (Position/Speed/TCM I believe). I'm going to replace these and see what happens next.

I'm not familiar with CAN, I purchased an Autel M806 Pro specifically to diagnose the car. Today was my first time using it. I'll check to see if it can give me more information.

Today was the first time it the car slipped while in AT and driving up the road. Wouldn't shift from 1st to 2nd (though it was earlier but only in AT and not Manual. Manual 1 and 3 worked, but never 2).

The car is new to me, I bought it a couple weeks ago.

Your response is very much appreciated. Thank you. A lot of help!