Test 3 Switch No. 2 Idle Tracking, (Codes 52 & 53)

NOTE: Observe the following instructions when performing the Subroutine Tests.


1. Do not measure voltage or resistance at the MCU module or connect any test light to it, unless otherwise instructed to do so.

2. Turn ignition key off and isolate both ends of a circuit whenever checking for shorts or continuity.

3. Connectors shown in schematics are viewed from front of connector.

4. Disconnect solenoids and switches from harness before checking continuity, resistance or by energizing by applying battery voltage directly.

5. Follow each step in order beginning with the first one in the appropriate routine. Follow each step until the problem is located, then correct the problem and perform the appropriate Functional Test to make sure that the problem has been corrected.

Fig.5 - MCU Wiring Circuit, Inlet Engines:

Test 3-Switch No. 2 Idle Tracking Switch (Codes 52 & 53)


NOTE: Make sure that throttle was off high cam and contacting Idle Tracking Switch during the Key On, Engine Off Test. If it was, continue with procedure. If not, repeat the Key On, Engine Off test to verify problem.


1. Check Idle Tracking Switch contacts to make sure that they are open when switch is actuated (closed throttle) and closed when not actuated (part throttle). If switch is okay, proceed to step 2. If not, proceed to step 4.

2. Check circuits 189 and 60 between ITS and MCU module for continuity, Fig. 5. Also check that circuit 189 is not shorted to ground. If circuits are okay, proceed to step 3. If a fault is found, service the affected circuit.

3. Check harness resistor by measuring resistance between circuits 189 and 687, Fig. 5 (with key off and ITS and module disconnected from harness). If resistance is within 280-380 ohms, replace MCU module. If not, replace resistor.

4. Reconnect ITS, then check harness resistor by measuring resistance between circuits 189 and 687, Fig. 5 (with key off and module disconnected from harness). If resistance is within 280-380 ohms, replace ITS. If not, replace resistor and ITS.