C0245 Code Speedometer stopped working, transmission wouldn't shift, abs and brake lights were on?

2004 CHEVROLET TRAILBLAZER

130,000 MILES • 4.2L • 4WD • AUTOMATIC

BAT KID

MEMBER
48 POSTS

I have a 2004 chevy trailblazer LT automatic 4WD with a 4.2 engine. Speedometer stopped working,transmission wouldnt shift,abs and brake lights were on. Codes were c0040,c0055 which were for front and rear abs circuit malfunction. The vehicle speed sensor was replaced along with the connector that plugs into it and 2 new wires from the vehicle speed sensor to the one ECM connector where the 2 wires go into because the old wiring had an issue in a tough spot to get to so i ran new wiring. Speedometer now works,transmission shifts normal. All codes went away but a new code appeared which is c0245 wheel speed sensor frequency error. I took the vehicle for a ride with my scanner on the live data for the ABS. When stopped the front and rear abs read 3.11 mph which i found online is normal for these older chevys. When driving the rear abs is reading approx 15-20mph lower than the front abs. For example the front will read 40mph but the rear will read 23mph. Speedometer will show whatever the rear is reading. The rear wheel speed sensor(located on the passenger side uptop of the transfer case towards the rear) was replaced. The issue is still the same so i’m under the assumption that there is a possible wiring issue with this sensor as well. The 2 wires(light blue and dark green) go to 1 of 3 connectors on the TCCM. Dark green wire is low signal-rear and light blue wire is high signal-rear. Is there a specific value i should be getting when testing these wires? I’m trying to figure out if there’s a wiring fault or a computer fault. Thank you

Jun 9, 2026 at 2:33 AM

STRAILER

✓ASE Certified Mechanic
54,832 POSTS

So I need to ask which seems correct the front or rear speed when you are actually driving the vehicle? Do both front wheel speed sensors read the same? Also, the value for the wire connections should be close to 0 ohms. I have seen metal on the reluctor ring cause this issue, I would remove the transfer case sensor and use a flashlight to check for metal contamination on the ring teeth. If that looks good I would try another abs control module, these go out often and with 130k that would be my next move. You can use this video to show you how.

https://www.youtube.com/watch?v=lUotkKXG9dY

Please let me know what happens.

Jun 9, 2026 at 4:26 PM

BAT KID

MEMBER
48 POSTS

The front is definitely correct with the speed of the vehicle and yes both front sensors read exactly the same. I will try what you said and look inside the hole where that sensor goes and see how those teeth look

Jun 9, 2026 at 5:28 PM

STRAILER

✓ASE Certified Mechanic
54,832 POSTS

Yep, little metal pieces can stick to the reluctor wheel and cause a misreading.

Jun 10, 2026 at 2:39 PM

BAT KID

MEMBER
48 POSTS

Sorry for the delay,so i used a scope inside that rear prop shaft hole,reluctor ring looks clean and fine no damage. Today i did live data on the transfer case and noticed an issue and this issue is the same whether its in 2WD,auto 4WD or 4HI,the rear prop shaft speed is reading but the ATC slip speed is reading the same exact rpm as the rear prop shaft and its showing red in color which obviously isn’t good and thinks it’s slipping. The front prop shaft speed is showing 0 rpm no matter what gear the transfer case is in and what speed im going so im assuming i either have a bad front prop shaft sensor or wiring issue to that sensor? And that could be why im having this speed issue with the rear abs n vss reading lower than the front abs?

Jun 27, 2026 at 8:15 PM

STRAILER

✓ASE Certified Mechanic
54,832 POSTS

I am not sure what you are says with the speed shaft sensor for the front drive shaft, there is none, do you mean the ABS wheel speed sensors? Also, did you swap out the ABS control module, these have a high failure rate.

Jun 28, 2026 at 4:28 PM

BAT KID

MEMBER
48 POSTS

Im attaching a picture and in the diagram,the one labeled #6 is the sensor im talking about. Its called (propshaft speed sensor-front) its reading 0 rpm at all times.I didnt swap out the abs module yet because im trying to rule out everything else first

Jun 28, 2026 at 5:18 PM

BAT KID

MEMBER
48 POSTS

Here is the picture

Image (Click to enlarge)

Jun 28, 2026 at 5:20 PM

STRAILER

✓ASE Certified Mechanic
54,832 POSTS

Gotcha, yes the front sensor does not control the speedometer, it is an input to the PCM. The sensor in the transfer case is the one that works for the speedo.

Jun 28, 2026 at 5:28 PM

BAT KID

MEMBER
48 POSTS

With that front sensor reading 0 rpm ,do you think that is playing a factor in the issue im having with the rear sensor only reading half of what the front abs sensors are reading or do you think its irrelevant? So if im going 45mph…the front abs sensors are reading 45mph but the rear sensor is reading 22mph and the vehicle speed sensor is reading the same 22mph because its using the same reluctor ring inside the case. The speedometer reads the 22mph on the dash. Obviously i feel like im going 45mph while driving so the front abs is definitely correct but the vehicle speed sensor and rear abs sensor are wrong. The drastic difference in what the front n rear abs readings are is setting that c0245 code. Im just not sure if the front prop sensor reading 0 rpm is relevant to this issue or if its just a module problem

Jun 28, 2026 at 5:40 PM

STRAILER

✓ASE Certified Mechanic
54,832 POSTS

I don't think the front sensor does much, but if the ABS module is bad it will give the bad readings you are getting for the front and rear differences. You can try to replace the front sensor again and also check for a reluctor wheel as well to be sure.

Jun 28, 2026 at 5:52 PM

BAT KID

MEMBER
48 POSTS

Okay im gunna try replacing that module and see what happens and recheck that ring i appreciate your help through this so far

Jun 28, 2026 at 5:54 PM

STRAILER

✓ASE Certified Mechanic
54,832 POSTS

Excellent! Let me know :)

Jun 28, 2026 at 5:59 PM

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