Test N: Step 4

4) Continuous Memory Codes 18, 28 or 48: Check IDM Circuit Continuity Code 18 indicates a loss of IDM input signal. Possible causes are:

Open harness circuit
Shorted harness
Faulty TFI or DIS module
Faulty ECA

Code 28 indicates the IDM input signal is always low. Possible causes are:

Open or shorted harness
Faulty CID sensor
VBAT (battery voltage) low at DIS
Faulty DIS module
Faulty ECA

Code 48 indicates IDM input signal always high. Possible causes are:

Open signal in harness
VBAT open at secondary coil
VBAT low at secondary coil

NOTE: On TFI vehicles the IDM circuit has a 22 k/ohm-resistor between Test Pin No. 4 and the ignition coil negative terminal (except 2.3L MA).

Turn key off an wait 10 seconds. Disconnect E-core ignition coil on TFI vehicles and DIS module connector (pins No. 7-12) on DIS equipped vehicles. Disconnect EDIS module (if equipped). Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leave ECA connected and set DVOM on 200-k/ohm scale.

On TFI equipped vehicles, measure resistance between Test Pin No. 4 at breakout box and negative terminal of ignition coil harness connector.

On DIS and EDIS equipped vehicles, measure resistance between Test Pin No. 4 at breakout box and DIS module harness connector pin No. 12.

If resistance is 20-24 k/ohms (on DIS and 2.3L MA, resistance should be less than 5 ohms), go to step 6) for EDIS vehicles or next step for all others. If resistance is not to specification, repair open circuit, clear codes, retest and reconnect "E" core coil.