Couple questions about HDC and possble issues with transmission
#31
11-04-2013, 12:59 PM
#32
11-04-2013, 01:39 PM
So far the speedo is working and still no 3 amigos. But my rear pads and rotors are pretty much bad and need to be replaced next week so im not sure if that could have anything to do with the HDC not working and this pending code. Ill have to see if anyone on here has a code reader I can borrow, either that or bring the truck to DAP enterprise, but im not insured at the moment so....
#34
11-04-2013, 02:26 PM
Pro Wrench
This comes from the RAVE:
Code:
ENGINE MANAGEMENT SYSTEM - V8 DESCRIPTION AND OPERATION 18-2-55Vehicle Speed Signal (VSS) The VSS is used, by the ECM, to control idle speed and overrun cut off. The ECM receives the signal through a hard wired connection direct from the SLABS ECU.For vehicles fitted with an automatic gearbox, two vehicle speed signals are received by the ECM. The second signal is derived from the main gearbox output shaft speed, and is sent to the ECM by the Electronic Automatic Transmission(EAT) ECU though the Controller Area Network (CAN).The ECM compares the vehicle speed signal generated by the SLABS ECU with that supplied via the CAN.The ECM also receives transfer box information. This allows the ECM to take in to account the vehicle being driven using low range gearing and compensate as necessary.On vehicles with manual transmission, the SLABS signal is checked against a threshold value stored in ECM memory.If other engine parameters indicate the engine is at high load and the VSS is below the threshold, a fault condition is registered in the diagnostic memory.The vehicle speed signal generated by the SLABS ECU is in the form of a pulse width modulated signal (PWM).Pulses are generated at 8000 per mile, and the frequency of the signal changes in accordance with road speed. At zero road speed the ECU outputs a reference signal at a frequency of 2Hz for diagnostic purposes.Function The input signal for the SLABS ECU is measured via pin 22 of connector C0637 of the ECM. The SLABS ECU generates a PWM signal switching between 0 and 12 volts at a frequency of 8000 pulses per mile. For vehicles with automatic gearbox the input signal for the EAT ECU is measured via pins 36 and 37 of connector C0637 of the ECM.These pin numbers provide a bi-directional communications link using the CAN data bus.In the case of a VSS failure on vehicles with automatic gearboxes, the ECM applies default values derived from the EAT ECU. There are no default values for manual gearbox vehicles.The VSS can fail in the following ways:Wiring short circuit to vehicle supply.Wiring short circuit to vehicle earth.Wiring open circuit.In the event of a VSS failure, any of the following symptoms may be observed:MIL illuminated after 2 driving cycles (NAS only).Vehicle speed limiting disabled (manual transmission vehicles only).SLABS/HDC warning lamp on and audible warning.Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook:P Code J2012 Description Land Rover Description P0500 Vehicle speed sensor malfunction VSS short or open circuitP0501 Vehicle speed sensor range/performance VSS implausibleRough road signalWhen the vehicle travels across rough terrain, or on rough roads instability becomes evident in the drive train. The ECM could interpret these vibrations as a 'false misfire'. To counteract this 'false misfire' the SLABS ECU generates a rough road signal, sends it to the ECM so that the ECM can suspend misfire detection for as long as the vehicle is travelling on the 'rough road'.
Last edited by SuperSport; 11-04-2013 at 02:31 PM.
#35
11-04-2013, 11:50 PM
This comes from the RAVE:
Code:
ENGINE MANAGEMENT SYSTEM - V8 DESCRIPTION AND OPERATION 18-2-55Vehicle Speed Signal (VSS) The VSS is used, by the ECM, to control idle speed and overrun cut off. The ECM receives the signal through a hard wired connection direct from the SLABS ECU.For vehicles fitted with an automatic gearbox, two vehicle speed signals are received by the ECM. The second signal is derived from the main gearbox output shaft speed, and is sent to the ECM by the Electronic Automatic Transmission(EAT) ECU though the Controller Area Network (CAN).The ECM compares the vehicle speed signal generated by the SLABS ECU with that supplied via the CAN.The ECM also receives transfer box information. This allows the ECM to take in to account the vehicle being driven using low range gearing and compensate as necessary.On vehicles with manual transmission, the SLABS signal is checked against a threshold value stored in ECM memory.If other engine parameters indicate the engine is at high load and the VSS is below the threshold, a fault condition is registered in the diagnostic memory.The vehicle speed signal generated by the SLABS ECU is in the form of a pulse width modulated signal (PWM).Pulses are generated at 8000 per mile, and the frequency of the signal changes in accordance with road speed. At zero road speed the ECU outputs a reference signal at a frequency of 2Hz for diagnostic purposes.Function The input signal for the SLABS ECU is measured via pin 22 of connector C0637 of the ECM. The SLABS ECU generates a PWM signal switching between 0 and 12 volts at a frequency of 8000 pulses per mile. For vehicles with automatic gearbox the input signal for the EAT ECU is measured via pins 36 and 37 of connector C0637 of the ECM.These pin numbers provide a bi-directional communications link using the CAN data bus.In the case of a VSS failure on vehicles with automatic gearboxes, the ECM applies default values derived from the EAT ECU. There are no default values for manual gearbox vehicles.The VSS can fail in the following ways:Wiring short circuit to vehicle supply.Wiring short circuit to vehicle earth.Wiring open circuit.In the event of a VSS failure, any of the following symptoms may be observed:MIL illuminated after 2 driving cycles (NAS only).Vehicle speed limiting disabled (manual transmission vehicles only).SLABS/HDC warning lamp on and audible warning.Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook:P Code J2012 Description Land Rover Description P0500 Vehicle speed sensor malfunction VSS short or open circuitP0501 Vehicle speed sensor range/performance VSS implausibleRough road signalWhen the vehicle travels across rough terrain, or on rough roads instability becomes evident in the drive train. The ECM could interpret these vibrations as a 'false misfire'. To counteract this 'false misfire' the SLABS ECU generates a rough road signal, sends it to the ECM so that the ECM can suspend misfire detection for as long as the vehicle is travelling on the 'rough road'.
Thanks for the link. Not trying to be a pain in the *** but I honestly did not understand half of it. Less tech explanation would be great. In any case Ive cleared the pending code twice so far..... it seems like whenever I engage the low range the code comes back and sometimes after speeding past 70mph it also comes on. So part of the description above seemed to imply to me that a fault in the VSS setup could cause HDC to flash with sound and as mentioned in another thread, when I engage low range and HDC the HDC flashed green with sound until its turned off. Also note that the low range/diff lock is sticking again cause its rough to shift and even after spraying lubricant on linkage I still cant engage diff lock.
So i found a write up on Discoweb that explains how to replace the VSS but I think its on a D1. Again Ive heard its been moved on the D2, can anyone confirm this? I really need to know what and where the part is located and what I have to do to fix the problem. Dont want to be left stranded and certainly dont want my vehicle shutting off on me while Im driving. I also think someone should make a thread on how to service a D2 VSS so it will be easier to find for future reference.
#36
11-05-2013, 12:31 PM
Pro Wrench
Thanks for the link. Not trying to be a pain in the *** but I honestly did not understand half of it. Less tech explanation would be great. In any case Ive cleared the pending code twice so far..... it seems like whenever I engage the low range the code comes back and sometimes after speeding past 70mph it also comes on. So part of the description above seemed to imply to me that a fault in the VSS setup could cause HDC to flash with sound and as mentioned in another thread, when I engage low range and HDC the HDC flashed green with sound until its turned off. Also note that the low range/diff lock is sticking again cause its rough to shift and even after spraying lubricant on linkage I still cant engage diff lock.
So i found a write up on Discoweb that explains how to replace the VSS but I think its on a D1. Again Ive heard its been moved on the D2, can anyone confirm this? I really need to know what and where the part is located and what I have to do to fix the problem. Dont want to be left stranded and certainly dont want my vehicle shutting off on me while Im driving. I also think someone should make a thread on how to service a D2 VSS so it will be easier to find for future reference.
So i found a write up on Discoweb that explains how to replace the VSS but I think its on a D1. Again Ive heard its been moved on the D2, can anyone confirm this? I really need to know what and where the part is located and what I have to do to fix the problem. Dont want to be left stranded and certainly dont want my vehicle shutting off on me while Im driving. I also think someone should make a thread on how to service a D2 VSS so it will be easier to find for future reference.
#37
11-05-2013, 12:57 PM
That would blow if it was the transfer case.... but now that I think about it I noticed long ago especially while driving on the highway that sometime as I remove my foot from the gas pedal I can hear a single mild clunk sound and a minor vibration. Its hard to replicate though. Do scanners have the capabilities of diagnosing the transfer case? I did free up the high low using some lub but i still cant engage the diff lock. I had to lub up the linkage when I first got the Disco to but after doing the job i was able to engage the diff lock as well. So not sure if its just a common rust build up issue thats making the linkage stiff or a mechanical issue with the transfer case itself.
Last edited by TRIARII; 11-05-2013 at 01:02 PM.
#38
11-05-2013, 01:05 PM
Pro Wrench
That would blow if it was the transfer case.... but now that I think about it I noticed long ago especially while driving on the highway that sometime as I remove my foot from the gas pedal I can hear a single mild clunk sound and a minor vibration. Its hard to replicate though. Do scanners have the capabilities of diagnosing the transfer case? I did free up the high low using some lub but i still cant engage the diff lock. I had to lub up the linkage when I first got the Disco to but after doing the job i was able to engage the diff lock as well. So not sure if its just a common rust build up issue thats making the linkage stiff or a mechanical issue with the transfer case itself.
#39
11-05-2013, 01:37 PM
I really need help here and would love to get this squared away but I dont have any additional info to provide at the moment. Have no idea where to go from here.
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