2003 Amazon ahc no power to relay (1 Viewer)

[Trb]

Hi guys this where I’m up to on ahc checks
Put another ahc ecu on and 5 codes have gone just leaving me with
C1731 height control front gate circuit
C1762 abnormal oil pressure to pump
Did some checks on gate valve plug all giving low reading except 2 to number 3 which is a pale purple coloured wire got zero
Also Nothing on accumulator solenoid plug
And dssh still blinking on of every second
And no sound from ahc pump
What’s your thoughts
Thanks terry

 

[Trb]

Late Edit: Pic of location of AHC IG fuse added.

One of my own basic mistakes is to forget to close all doors and the rear hatch on the vehicle when doing AHC tests. If any of these are open, the AHC system is prevented from operating for safety reasons. The system is interlocked with the door switches. It is OK if the engine hood is open – because there is no interlock switch here.

As already mentioned by @suprarx7nut , it is important to start the investigation by clearing the Diagnostic Trouble Codes (DTC’s) which may have accumulated in the Electronic Control System (ECU) memory. If some DTC’s return after clearing, then that indicates real ongoing faults which will need to be resolved.

Suggest post these ongoing faults on this IH8MUD thread so that Members can offer further comments:

There are several ways to clear DTC’s:

Use the clearing function on the handheld device or Techstream.

If unsuccessful, use the manual method described at Post #6 at this link to clear DTC’s:
AHC wont raise after battery out - https://forum.ih8mud.com/threads/ahc-wont-raise-after-battery-out.1250534/#post-13814584

Alternatively, try re-booting the system. To do this, disconnect the battery or batteries and allow the system to power down, then re-connect the battery or batteries and re-start.

A fluid leak was mentioned. If the AHC Pump ran dry even if only momentarily, it will have stopped momentarily, at least until it was re-primed with AHC Fluid. In this case, these Diagnostic Trouble Codes (DTC) may be recorded by the ECU and will need to be cleared:
C1751 – AHC Pump & Motor
C1762 – Pressure Malfunction

It is also possible that an electrical disruption such as ‘jump starting’ may cause the AHC Main Relay to stop and show this DTC:
C1743 – AHC Main Relay Function
Some hints on overcoming this problem are found at Post #1 by @PADDO at this link:
AHC DTC C1743 - main relay - https://forum.ih8mud.com/threads/ahc-dtc-c1743-main-relay.914138/
(Refers to AHC IG fuse which is found here -- behind cover in Left Hand footwell):
View attachment 2673836

Hopefully, you will not see the DTC which indicates malfunction of the ECU. If it appears, it indicates that the ECU has stopped due to internal memory errors. This requires replacement of the ECU. The AHC system will not work correctly and may not work at all with a faulty ECU.
C1761 – Malfunction of ECU

If you wish to explore the "Diagnostic Section" and "On-vehicle Section" of the Factory Service Manual (FSM) for Active Height Control (AHC) and the Toyota Electronic Modulated Suspension (TEMS), then the following are useful references:

AHC Diagnostics:
https://lc100e.github.io/manual/
At this link, use the Index on the left hand side of the opening page and follow these tabs:
Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL & SKYHOOK TEMS

AHC On-Vehicle Inspection including correct AHC pressure ranges:
https://lc100e.github.io/manual/
At this link, use the Index on the left hand side of the opening page and follow these tabs:
Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM (Independent Front Suspension) > ON-VEHICLE INSPECTION

Hope this gives you a few thought-starters!

Hi there did you see my last post hope you can help not sure where to go with this next
Thanks for you’re help so far

 

[IndroCruise]

Hi there did you see my last post hope you can help not sure where to go with this next
Thanks for you’re help so far

Suggest go to

AHC Diagnostics:
https://lc100e.github.io/manual/ -- the Factory Service Manual (FSM)
At this link, use the Index on the left hand side of the opening page and follow these tabs:
Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL & SKYHOOK TEMS

Then at the list here, go to C1731 to C1736 and also to C1762 (Aug 2000 onwards)

Where “Active Test” is mentioned, use the manual method described at Page 6 in the attachment to Post #17 in this thread – this uses DLC1 in the engine bay and is easier than the method using DLC3.

C1731 Front Gate Valve Circuit in the Control Valve Assembly

It appears that this part of the Control Valve Assembly is not working, although it is not clear why. Problems in the Control Valve Assembly are rare, not often seen on IH8MUD – suggest try a search under “Control Valve Assembly” and “Gate Valve”. The Gate Valves (one for Front, one for Rear) control the hydraulic connection between the Left and Right sides of the vehicle, separately at Front and Rear. These Valves operate when the vehicle is cornering. Otherwise the Gate Valves are meant to remain open when steering is straight ahead, or when the vehicle is stationary.

If not already done, suggest use a multimeter and perform the tests mention in this section of the FSM. The purpose of the test is to check the condition of the solenoids which operate the Valves by testing continuity of the circuit. If there is an open circuit, then the relevant solenoid is defective. If so, that would require replacement of the Control Valve Assembly.

Before replacing anything, physically inspect the actual visual condition of the actual connector to the Control Valve Assembly. Also check the voltage which is being being received at the this connector using a multimeter and check continuity back through the harness. The point is that this connector is quite exposed to underbody conditions – road grit, stones, sticks, water, snow, etc. Damage to the connector is quite possible and a damage connector can be responsible for this DTC.

The connector to the Control Valve Assembly can be difficult to remove and difficult to see properly. It may be covered by a loose shroud. The connector is the same style as the connector to the windscreen wiper motor in the engine bay – much easier to see and easier to work out how to unlock it.

C1762 Fluid Pressure Abnormality (Pump does not supply Fluid)

If not already done, perform the tests mentioned in this section of the FSM. In particular, check whether the pump can be operated by direct connection to the battery in the manner described.

Even though not showing as DTC’s, also check the following:

C1718 Fluid Pressure Sensor Circuit
C1741 AHC Motor Relay Circuit
C1743 AHC Main Relay Cirfuit
C1751 AHC Pump & Motor Circuit
C1763 Fluid Pressure Abnormality

 

[Trb]

Suggest go to

AHC Diagnostics:
https://lc100e.github.io/manual/ -- the Factory Service Manual (FSM)
At this link, use the Index on the left hand side of the opening page and follow these tabs:
Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL & SKYHOOK TEMS

Then at the list here, go to C1731 to C1736 and also to C1762 (Aug 2000 onwards)

Where “Active Test” is mentioned, use the manual method described at Page 6 in the attachment to Post #17 in this thread – this uses DLC1 in the engine bay and is easier than the method using DLC3.

C1731 Front Gate Valve Circuit in the Control Valve Assembly

It appears that this part of the Control Valve Assembly is not working, although it is not clear why. Problems in the Control Valve Assembly are rare, not often seen on IH8MUD – suggest try a search under “Control Valve Assembly” and “Gate Valve”. The Gate Valves (one for Front, one for Rear) control the hydraulic connection between the Left and Right sides of the vehicle, separately at Front and Rear. These Valves operate when the vehicle is cornering. Otherwise the Gate Valves are meant to remain open when steering is straight ahead, or when the vehicle is stationary.

If not already done, suggest use a multimeter and perform the tests mention in this section of the FSM. The purpose of the test is to check the condition of the solenoids which operate the Valves by testing continuity of the circuit. If there is an open circuit, then the relevant solenoid is defective. If so, that would require replacement of the Control Valve Assembly.

Before replacing anything, physically inspect the actual visual condition of the actual connector to the Control Valve Assembly. Also check the voltage which is being being received at the this connector using a multimeter and check continuity back through the harness. The point is that this connector is quite exposed to underbody conditions – road grit, stones, sticks, water, snow, etc. Damage to the connector is quite possible and a damage connector can be responsible for this DTC.

The connector to the Control Valve Assembly can be difficult to remove and difficult to see properly. It may be covered by a loose shroud. The connector is the same style as the connector to the windscreen wiper motor in the engine bay – much easier to see and easier to work out how to unlock it.

C1762 Fluid Pressure Abnormality (Pump does not supply Fluid)

If not already done, perform the tests mentioned in this section of the FSM. In particular, check whether the pump can be operated by direct connection to the battery in the manner described.

Even though not showing as DTC’s, also check the following:

C1718 Fluid Pressure Sensor Circuit
C1741 AHC Motor Relay Circuit
C1743 AHC Main Relay Cirfuit
C1751 AHC Pump & Motor Circuit
C1763 Fluid Pressure Abnormality

Hi done the plug check to gate valve
No continuity from number 2 to number 3 the pale pinky coloured wire
All the rest showing continuity
What’s your thoughts on this
Thanks terry

 

[Trb]

Hi guys sorted the gate valve issue one wire from gate valve to rear plug had failed put new wire in blinking light now gone off
All dtc have cleared
But lc has risen high and will not lower
Also had to top up fluid
And when I checked fluid again it was very low
But no leaks
If spheres are shot would they just fill with fluid
Hope you
Can help cheers Terry

 

[IndroCruise]

Hi guys sorted the gate valve issue one wire from gate valve to rear plug had failed put new wire in blinking light now gone off
All dtc have cleared
But lc has risen high and will not lower
Also had to top up fluid
And when I checked fluid again it was very low
But no leaks
If spheres are shot would they just fill with fluid
Hope you
Can help cheers Terry

It seems like you have had some good success but the vehicle now is at “HI” height and won’t lower again ….

Can you please confirm that the AHC Pump has been running??

Please advise what all of your Height Sensor readings are right now, using your scanner, with vehicle on a level surface – Front Right, Front Left and Rear???

Please also advise what your hub-to-fender heights are at each wheel right now, measured using tape-measure from the centre of the wheel-hub to the fender lip immediately above, with vehicle on a level surface – all four wheels???

Way back in your Post #13, your Picture #6 and Picture #8, shows some Height Sensor readings:

Front Right: -81.6mm
Front Left_: +28.8mm
Rear_______: -65.8mm

These look like readings at “LO” height, before you overcame some of the recent problems??

Difference between Front Right and Front Left is 110.4 mm
Difference between Front Left and Rear is 94.6 mm

These are VERY BIG DIFFERENCES.

What are the scanner readings now? What are the hub-to-fender tape-measurements now?

The point is that if the vehicle is level side-to-side, then Height Sensor readings like this are impossible

• unless the Height Control Sensors are way out of adjustment, or,
• unless one or more Height Control Sensors are faulty.

In either case, if the Electronic Control Unit (ECU) is healthy and receiving signals with such large differences from the Height Control Sensors, then the ECU will put the AHC system into ‘fail safe mode’ and it will refuse to move up or down.

Height Control Sensors which are faulty or way out of adjustment also will cause strange behaviour, like the Front or Rear raising too much.

Anyway, to go further please give the actual requested measurements. Please do not just say that the vehicle is level or that the measurements are OK. The actual data is needed.

By the way, the fluid level in the AHC Tank is expected to be low when the vehicle is at “HI” height because the fluid has been sent to the ‘shock absorbers’, either by the AHC Pump or by the Height Control Accumulator or both. This is what causes the vehicle to raise.

When the system is working again, you will be able to test the overall condition of the ‘spheres’ using the procedure in the attachment – leave this until later -- it cannot be done until you can raise and lower the vehicle using the AHC system.

Your replies to the above questions will help our understanding of your vehicle and how best to move forward.

 

[Trb]

It seems like you have had some good success but the vehicle now is at “HI” height and won’t lower again ….

Can you please confirm that the AHC Pump has been running??

Please advise what all of your Height Sensor readings are right now, using your scanner, with vehicle on a level surface – Front Right, Front Left and Rear???

Please also advise what your hub-to-fender heights are at each wheel right now, measured using tape-measure from the centre of the wheel-hub to the fender lip immediately above, with vehicle on a level surface – all four wheels???

Way back in your Post #13, your Picture #6 and Picture #8, shows some Height Sensor readings:

Front Right: -81.6mm
Front Left_: +28.8mm
Rear_______: -65.8mm

These look like readings at “LO” height, before you overcame some of the recent problems??

Difference between Front Right and Front Left is 110.4 mm
Difference between Front Left and Rear is 94.6 mm

These are VERY BIG DIFFERENCES.

What are the scanner readings now? What are the hub-to-fender tape-measurements now?

The point is that if the vehicle is level side-to-side, then Height Sensor readings like this are impossible

• unless the Height Control Sensors are way out of adjustment, or,
• unless one or more Height Control Sensors are faulty.

In either case, if the Electronic Control Unit (ECU) is healthy and receiving signals with such large differences from the Height Control Sensors, then the ECU will put the AHC system into ‘fail safe mode’ and it will refuse to move up or down.

Height Control Sensors which are faulty or way out of adjustment also will cause strange behaviour, like the Front or Rear raising too much.

Anyway, to go further please give the actual requested measurements. Please do not just say that the vehicle is level or that the measurements are OK. The actual data is needed.

By the way, the fluid level in the AHC Tank is expected to be low when the vehicle is at “HI” height because the fluid has been sent to the ‘shock absorbers’, either by the AHC Pump or by the Height Control Accumulator or both. This is what causes the vehicle to raise.

When the system is working again, you will be able to test the overall condition of the ‘spheres’ using the procedure in the attachment – leave this until later -- it cannot be done until you can raise and lower the vehicle using the AHC system.

Your replies to the above questions will help our understanding of your vehicle and how best to move forward.

Ok got a few things to check
Thanks for you’re time cheers