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ABS warning light NOT functional

Joined
11 January 2007
Messages
115
Location
Hong Kong
1993 AT to MT conversion RHD NA1:

Most posts on ALB/ABS issues relate warning light ON and how to turn it off. The problem we are having is lack of ABS warning light when the system is clearly non-functional. Am stumped, hoping to get some direction.:confused:
  • The ABS system has the common ticking/stuck valves so plan is to upgrade to the NA2 system. But a non-functional ABS warning light is a safety issue.
  • It's not the bulb. The ABS light cycle check on/off at start up works fine.
  • There are no codes, with SCS shorted - ABS yellow warning light stays on solid.
  • When the handbrake is purposely left on in attempt to trigger the TCS and ABS, only the TCS warning comes on. When the TCS triggers, the ABS shuts down at exactly the same time.
  • Have checked whether the pressure sensor (yellow/ black – orange connector) has been shorted to disable the ABS warning light and it has not.
  • Unplugging the ABS pump connector did not trigger an ABS warning. With the connector disconnected and ignition on the ABS light still checks/cycles on then off. No ABS light during test drive either. System still had some pressure in it so ABS worked a couple times (with pump disconnected) then shut down.


Thanks in advance!
 
Mine does the exact same thing. Interested to know the outcome.
 
Probably best to summon the abs guru for this one. [MENTION=25737]Kaz-kzukNA1[/MENTION] any advice sir?
 
Although you already confirmed it through the 30sec parking brake method, to be 100% sure, please disconnect one of the four orange connector of the solenoids near the ABS modulator and start the engine.
Is the ABS light triggered?

Regardless of whether the ABS light triggered or not, please read the error code using the blue 2pin SCS terminal method.
Did you get any codes starting with 7-*?

If the answer to both question is no, then several possibilities.


1. How is the ABS controller installed?
Is it securely mounted inside the metal rack with the metal bolts at the corners and also the rack bolted to the bulkhead?
Please remember that the ABS controller uses its housing/case itself as the GND so it must be bolted down to the chassis GND.

2. Fuse ABS2,3?

3. If you are 100% sure that your NSX is 93 model, then when you disconnect both orange connectors from the ABS controller and start the engine, what will happen to the ABS light?
This is to check whether someone installed simple relay circuit with R-C time constant of about 2sec to defeat the ABS warning light circuit or not.


Should be enough to start with.


Kaz
 
Kaz, thank you for your response and recommendations. Answers below:

Kaz-kzukNA1
Although you already confirmed it through the 30sec parking brake method, to be 100% sure, please disconnect one of the four orange connector of the solenoids near the ABS modulator and start the engine.
Is the ABS light triggered?


Disconnected one connector and started engine. ABS light test cycle on/off then stayed off. No warning light triggered.

Regardless of whether the ABS light triggered or not, please read the error code using the blue 2pin SCS terminal method.
Did you get any codes starting with 7-*?


No codes from the SCS. ABS light stays on solid.

If the answer to both question is no, then several possibilities.


1. How is the ABS controller installed?
It is securely mounted inside the metal rack with the metal bolts at the corners and the rack bolted is also bolted to the bulkhead.

20170411_130955.jpg

2. Fuse ABS2,3?
Fuse is not blown. When pulled out and engine started, the TCS warning light will stay on. ABS light is off. SCS doesn't show any codes however (car not driven, just started and idled).

3. If you are 100% sure that your NSX is 93 model...

This is what a VIN decoder revealed. Non-USDM car and unsure what relevant codes are for year of manufacture. 10th position, is a "0". Looks like it's an original MT car with power steering vs. an AT to MT conversion.
field value description
country J Japan
manufacturer H Honda
make 4 Passenger car, gasoline engine
engine NA1 3.0L (C30A)
body & transmission 1 2-door manual
trim 6 1997+ NSX-T with Power Steering, Driver Airbag, Active Belt
check digit 0 okay
model year 0 invalid. must be: 1,2,3,4,5,6,7,8,9,M,N,P,R,S,T,V,W,X,Y,A,B,C,D,E,F
assembly plant T Tochigi, Japan
serial number 200028 okay


... then when you disconnect both orange connectors from the ABS controller and start the engine, what will happen to the ABS light?
This is to check whether someone installed simple relay circuit with R-C time constant of about 2sec to defeat the ABS warning light circuit or not.


With both orange connectors at ABS module unplugged and engine started - the ABS light is still off. TCS is triggered and code for it is 4-9 for all wheel sensors. With system code memory cleared and connectors reconnected, TCS is normal, no codes.

Found the OEM harness had been modified. This is the harness between the ignition tumbler and a brown connector plug. Location is underneath steering wheel (RHD) on wheel well side. Believe the brown connector goes to the fuse/relay box in front.
Looks like a relay and resistor have been added, it T's into the harness between the ignition switch & brown connector. When the relay is disconnected, no power gets to the starter. Seems like some kind of security system, not sure if this can affect the ABS warning light. Here's an image of it.

What harness is the 2 sec defeat relay normally tapped into?

Thank you for your help.

20170411_131458.jpg
 
Not sure what Tapatalks are doing these days as they seem to introduce new issues when trying to fix something else…..
I use it for monitoring new posts/threads but not easy compared to old versions....

Any way, got extra info from you and based on these, I can confirm the followngs;

ABS does work under hard braking and it produces brake pedal kick back several times.

After this, if the accumulator loses pressure below the threshold, the ABS pump will kick in and re-pressurise the system.

ABS light bulb works at least during the light bulb check mode.

However;
Disconnecting one of the solenoid connector didn’t trigger the ABS light even after starting the engine despite it being part of the initial diag sequence.

After this, reading the error code didn’t show anything. No code stored.


Based on these, the main and part of the sub controllers are working but question mark on the rest of the sub controller. There is also slim chance of wiring modifications done in order to prevent the ABS light being triggered (even if it was detected) and also clearing the error code on purposely through the wiring modifications. I saw one NSX with such modifications on EPS controller circuit so it can be done.

My recommendation is to try another known good ABS controller first.
If it shows the same issue, then I’m afraid you need to look at the chassis loom and ABS warning light circuit to find out what kind of modifications were done.

Kaz
 
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