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Home >> Toyota >> 2002 >> Corolla CE, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 47 (Automatic Transmission Diagnosis - U340E & U341E) >> Diagnostic Tests >> DTC P1790: Shift Solenoid St Circuit Malfunction >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Toyota ECHO, 2002 Toyota Celica, 2001 Toyota ECHO, and 2001 Toyota Celica. However, it is still accessible from the selected car via links, so may be relevant.
  1. Access the ECM, located in engine compartment, near battery on Celica, and behind glove compartment on ECHO. See Figure and Figure . Disconnect appropriate ECM connector for terminal ST. See Figure and Figure . Using a DVOM, check continuity between ground and ECM connector terminal ST. If resistance is 11-15 ohms, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. If resistance is not within specification, go to next step.
  2. Disconnect transaxle solenoid connector located above PNP switch, on side of transaxle. Using a DVOM, check for continuity between terminal ST at ECM connector and terminal No. 2 at transaxle solenoid connector. See Figure-Figure . If continuity exists, go to next step. If continuity does not exist, inspect and repair circuit(s) as necessary.
  3. Raise and support vehicle. Remove transaxle oil pan. See LUBRICATION in appropriate SERVICING article. Disconnect shift solenoid ST connector. See Figure. Using a DVOM, measure resistance between solenoid body and solenoid connector terminal. If resistance is not 11-15 ohms, replace solenoid. If resistance is 11-15 ohms, repair wiring harness or connector between ECM and solenoid. To check solenoid operation, go to next step.
  4. Remove solenoid from valve body. Connect positive lead from battery to solenoid terminal. Connect negative lead to solenoid body. With power supplied to solenoid, ensure solenoid valve makes an operating sound. If solenoid does not operate as described, replace solenoid. If solenoid operates as described, go to next step.
  5. Check solenoid seals, connect battery voltage to solenoid. Apply 71 psi (5 kg/cm2 ) of compressed air to solenoid with battery voltage connected. With battery voltage applied, air should pass through solenoid. Disconnect voltage to solenoid. Ensure air does not pass through solenoid. See Figure. Replace solenoid if defective. If okay, go to next step.
  6. Check and repair wiring harness or connector between solenoid and ECM. If wiring harness and connector are okay, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
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