Evaporative Emissions System: Testing and Inspection

NOTE: Since the Evaporative Emission System is controlled by the Motronic Engine control unit it may be necessary to review procedures concerning the On-Board Diagnostics and Fault Codes in COMPUTERIZED ENGINE CONTROLS to properly complete this procedure.


Perform the following test procedure using a suitable digital volt/ohmmeter, referring to Fig. 3 for terminal identification.

Fig. 3 Bosch Motronic Electronic Engine Control System Terminal Identification:

1. Inspect all system components, lines and connections for damage.
2. Perform procedure described under ``Output-Periphery Test'' for TEV. If audible Tick-Tock sound is not heard, proceed as follows:
a. Locate TEV at the lefthand side firewall above the master cylinder.
b. Disconnect TEV electrical connector.
c. Check TEV winding resistance should be 37-53 ohms at 64-82°F. Replace valve if reading is not as specified.
d. Inspect TEV connector terminals and ECU terminal 31.
e. With ignition key in Run position, check battery voltage is present at TEV connector terminal 43 and main relay terminal 87. If battery voltage is not present, check connection to main relay.

Fig. 10 ECU TEV Signal:

f. With engine running, use a suitable oscilloscope to check ECU TEV signal is as shown Fig. 10. If signal is not as specified, replace ECU.
3. Check TEV for leakage as follows:
a. Remove valve from vehicle.

Fig. 11 TEV & TES Valve Connector Identification:

b. Connect vacuum pump to intake manifold port connection No. 2, Fig. 11. No vacuum reading should be achieved.
c. Apply 12 volts to TEV. Vacuum pump should hold at 7.25 psi and exceed 3.6 psi after 10 seconds.
d. Remove 12 volt supply from TEV, then plug port No. 1. Vacuum pump should hold at 7.25 psi.
4. Check TES for leakage as follows:
a. Locate valve at the lefthand side firewall above the master cylinder, then remove valve from vehicle.

Fig. 11 TEV & TES Valve Connector Identification:

b. Connect vacuum pump to intake manifold port connection No. 2, Fig. 11. Vacuum pump should hold at 7.25 psi.
c. Apply 12 volts to TEV. No vacuum reading should be achieved.
5. Check TES winding resistance should be 37-53 ohms. Replace valve if reading is not as specified.
6. With ignition key in the Run position, check battery voltage is present at TES connector. If voltage is not present, check connection to main relay terminals 85 and 87.