The ABS and TRAC warning light on my T5R has lighted up lately, just weeks after the replacement of the master brake booster. I have checked the fault code and it show that the TRAC pressure sensor, peddle position sensor and brake light sensor faulty. I can locate the last two sensors but please if anyone can advise me where is the TRAC pressure sensor. Seen lots of mail about ABS module failure and if that is likely? It is also suspected that the hydraulic system has not been thoughfully bleeded. Would water vapour in brake fluid damage ABS system?

Also, the air-cond would fail whenever after a traffic jam in hot weather. If that can be cured? (Air-cond is very cool while the car is running)

Looking forward to have reply and hope the problem can be solve soon as I am starting to lose confident on Volvo after driving it for 6 months and having so many problems.

Does the fan behind the radiator come on when you turn the A/C ON ? If the fan isn't coming on you'll overheat the engine and you won't get airflow to cool the A/C condenser while the car is stopped. If you post your email I will send you the shop manual instructions for troubleshooting the TRACS system, but its too long to post here (too many diagrams too).

DTC 4-2-4: TRACS PRESSURE SWITCH, OPEN OR SHORT CIRCUIT:

1) This DTC is set when control module senses pressure switch
has been shorted or grounded. Connect test box to control module. See
Fig. 3. Check pressure switch by connecting an ohmmeter between test
box terminals No. 13 and 26. Ohmmeter should indicate zero ohms.
Connect ohmmeter between test box terminal No. 26 and ground. Ohmmeter
should indicate no continuity.

2) If any reading is incorrect, check if wiring is broken or
shorted. If wiring is okay, replace hydraulic modulator. If readings
are correct, go to next step.

3) Connect an ohmmeter between test box terminals No. 13 and
26. Depress brake pedal. If ohmmeter indicates no continuity, ensure
brakelight contact is operating. If brakelight contact is okay, erase
DTC and test drive vehicle. See TEST DRIVING VEHICLE under DIAGNOSIS &
TESTING. If DTC reoccurs, replace control module. If ohmmeter
indicates continuity, check wiring for a short circuit. If a short
circuit is not present, replace hydraulic modulator.


Mike

Fisrst of all, thanks for your help and hey, Mr Hamfisted is really a pro.
My e-mail address is: herman.choy@towngas.com
Look forward to receive the shop manual.
The radiator fan does come on. The A/C stop usually just after the jam is cleared, where the acuminated heat from the engine release into the engine compartment.