Reading wrong

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Mar 31, 2014 | 07:13 PM

metalheadbusa

Thread Starter

Instructor

Joined: Jul 2012

Posts: 115

Likes: 1

From: Mayfield Ky

Reading wrong

Hello everyone . I put the replacement BCM in and the steering colum lock appeared so I order the lmc5 mod that fixed that. Now my speedometer is reading wrong can anyone help me with this little bug?

Mar 31, 2014 | 08:09 PM

65GGvert

Team Owner

Joined: Jul 2006

Posts: 22,109

Likes: 4,137

From: Kannapolis NC

Why not share some information, like what year car, how much off is the speedometer? Was the speedometer correct before you replaced the BCM?

Mar 31, 2014 | 08:38 PM

metalheadbusa

Thread Starter

Instructor

Joined: Jul 2012

Posts: 115

Likes: 1

From: Mayfield Ky

The car is a 99 c5 yep it was correct before I put in the BCM and it's reading about 15-20 miles off . Speedo says I'm doing 45 when I'm really going 60

Mar 31, 2014 | 08:49 PM

lionelhutz

Race Director

Joined: Apr 2007

Posts: 11,150

Likes: 890

From: South Western Ontario

You've got an interesting problem. The PCM provides a PWM output signal directly to the cluster for the speedometer and the PCM is where you program for gear or tire changes so there is no reason why the BCM would affect the speedometer.

Apr 1, 2014 | 10:17 AM

dadaroo

Le Mans Master

Joined: Mar 2011

Posts: 6,835

Likes: 301

From: Columbia SC

Let me scratch my head on this.

If I recall, you dumped a lot of heater coolant into the passenger foot well. May have affected that circuit somehow. Will look at the FSM design and routing later.

If I recall the speed signal to the IPC is based on pulses and not voltage.

Could be an unrelated problem with the VSS sensor or circuit/PCM.

If I were you, I would printout a copy of this in case you get pulled over. Could not hurt to help get a warning and not a ticket until we figure out what is wrong.