Too slow speed in speedo - P38

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kaisersoze

New Member
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12
Location
Bergen, Norway
Hi!

I recently purchased a 1996 P38 DSE. The car had a cracked engine block, so I have replaced the engine with great success:) Unfortunately the car have two problems that still have not been resolved:

1. The speedometer shows the wrong speed. Up to 40 km/h (approx 25 mph) the speed is correct. Hereafter the speedo is significantly slower than actual speed. At 70 km / h the speedo shows about 50 km/h and 80 km/h the speedo shows around just below 60 km / h. The other instruments in the display is functioning ok. Does anyone have experience with this type of error?

2. I also have problem when shifting the transferbox to low. The selector symbol in the display is beeping forever and the transferbox will not switch over. I have changed my H / L motor without result. The gear selector lights is flashing and I have (the common) "select neutral" message. I've disabled the transfer ECU and I didn't spotted any burned components. Should I try replacing the ECU anyway?

Can there be a connection between these errors?

Thanks in advance for any help!
 
Last edited:
Only guessing here, but from my Rovacom, I can switch between mph & kph, so I wonder if yours has somehow changed from kph to mph??
If it were reading mph on a kph clockface, then it would show the needle at an apparent slower speed??

As for the hi-lo, I had a ecu burn out a few years back, & left me in lo range, so to get me out of trouble & going again, I connected a battery to the selector motor with jump-leads & manually powered it back to hi, this also showed on the display, so try this yourself, if it DOES change the ratios, then the motor is ok & you can look at the ecu, selector switch or wiring.
Merry Christmas.
 
kaisersoze said:
Hi!

I recently purchased a 1996 P38 DSE. The car had a cracked engine block, so I have replaced the engine with great success:) Unfortunately the car have two problems that still have not been resolved:

1. The speedometer shows the wrong speed. Up to 40 km/h (approx 25 mph) the speed is correct. Hereafter the speedo is significantly slower than actual speed. At 70 km / h the speedo shows about 50 km/h and 80 km/h the speedo shows around just below 60 km / h. The other instruments in the display is functioning ok. Does anyone have experience with this type of error?

2. I also have problem when shifting the transferbox to low. The selector symbol in the display is beeping forever and the transferbox will not switch over. I have changed my H / L motor without result. The gear selector lights is flashing and I have (the common) "select neutral" message. I've disabled the transfer ECU and I didn't spotted any burned components. Should I try replacing the ECU anyway?

Can there be a connection between these errors?

Thanks in advance for any help!
Click to expand...

It doesn't have big wheels on by any chance does it?
 
Thanks for the replies!

The car has standard 235 70 16 tires fitted. The ABS sensors also seems to work ok. Does anyone know were the speed o get the signal from? Is it the ABS sensors through the BECM?

The speed is correct up to 25 mph, so I don't think kmh and mph have been switched in the BECM (I have not bought a Faultmate yet, so I can't check...)

Thanks for the tips regarding jump-lead & manually power the hi/low motor. I will try this out
 
the speed sensor is from a unit at the top of the transfer box by the transmission brake.
check all the plugs around there.
 
kaisersoze said:
Thanks for the replies!

The car has standard 235 70 16 tires fitted. The ABS sensors also seems to work ok. Does anyone know were the speed o get the signal from? Is it the ABS sensors through the BECM?

The speed is correct up to 25 mph, so I don't think kmh and mph have been switched in the BECM (I have not bought a Faultmate yet, so I can't check...)

Thanks for the tips regarding jump-lead & manually power the hi/low motor. I will try this out
Click to expand...
Did you ever get this speedo issue sorted out? Mine has been doing this since we bought it a month or so ago, although checking it against GPS it was accurate again at 70mph, which was weird. Someone suggested one of the adjuster pots could be dying as that might affect it - if so I think it has now gone toes up as total speedo failure today.
 
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