[asthmamax11]

Was driving and CEL turns on
Rev match feature doesn't turn on
Rear camera doesn't turn on

P18C4 gear position sensor low voltage

U0401-71 anti-lock brakes


Car is 6 speed with 38k miles
Magnuson supercharged for over 10k miles no issues

Anyone else have experience with these codes ?

[arpad_m]

Weak battery perhaps? These issues are unrelated, and the codes popping up at the same time indicate a potential electrical problem, so the first thing I'd check on the cheap would be the battery.

[asthmamax11]

Originally Posted by arpad_m

Weak battery perhaps? These issues are unrelated, and the codes popping up at the same time indicate a potential electrical problem, so the first thing I'd check on the cheap would be the battery.

Well I replaced the battery about 8 months ago
I don't drive the car more than about three times a month though

I'll get it tested my next day off

[SSgtSS1LE]

Check the wiring harness for short to ground between sensor and ECM. Both codes should clear, not return, and current gear should display once short is repaired.

DTC Descriptor: Invalid Data Received From ECM
DTC: U0401
Some devices are constantly receiving information from other devices through serial data communication network. The invalid data code will be set when a receiving device detects a discrepancy in information it receives from another device causing its integrity to be questioned. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

Symptom Byte: 71
Invalid Data - This sub type is used by the Electronic Control Unit to indicate a signal was received with the corresponding validity bit equal to invalid or post processing of the signal determines it is invalid.

Circuit: Gate Select Position (Gear Position Sensor, number 3)
DTC: P18C4 - Short to Ground



Circuit/System Description
The gate select position sensor is a switching transistor mounted to the transmission extension housing. The four wire sensor interfaces directly with the Engine Control Module (ECM). The ECM supplies 5 volts to the Gate Select Position sensor on a 5 volt reference circuit and also provides a ground path on a low reference circuit. The sensor provides a Pulse Width Modulated (PWW) duty cycle to the ECM on two signal circuits that are proportional to the linear and radial position of the corresponding magnet assembly mounted to the shift shaft. The vehicle uses the gear position sensor information primarily for Active Rev Matching and Active Fuel Management. The ECM monitors the radial position signal 1 circuit for low and high voltage conditions.

[asthmamax11]

Thank you for detailed diagram and highlighting the two culprits.
I appreciate you taking time to help.

[Ruthless Camaro]

Originally Posted by asthmamax11

Was driving and CEL turns on
Rev match feature doesn't turn on
Rear camera doesn't turn on

P18C4 gear position sensor low voltage

U0401-71 anti-lock brakes


Car is 6 speed with 38k miles
Magnuson supercharged for over 10k miles no issues

Anyone else have experience with these codes ?

I just bought a 2017 2SS M6 and I’ve only had it for 2 days until my check engine light came on along with the service parking break, I also noticed my rev match, reverse camera, cruise control, blind spot monitoring, drive modes, and my exhaust sound selector was not working, I took it to autozone for a scan and these codes popped up, P0735, incorrect 5th gear ratio, Secondary DTCs
•P0734: 4th gear ratio incorrect
•P18C6: Gear position sensor circuit 2 low voltage.
-U0401-71: invalid data received from engine control module-invalid data


So I took it chevy and it looks like the gear selector position sensor needed replacement, good thing I didn’t have to pay for it cause it was covered, but the service advisor said it was $1400, still waiting for the part and my car is still at the service. Did you ever get this issue solved?

[Summit20171SS]

Im having this same issue with codes P0735 and P0729 which is 5th and 6th gear