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Pinpoint Test B: Code 212 Or 226

  1. Check IDM Signal At ICM  With ignition off, install EI diagnostic cable to breakout box and ICM. DO NOT connect CKP sensor tee or coil tees. Use EI "6" overlay on breakout box. Connect EI diagnostic cable negative and positive leads to battery. Set EI diagnostic cable box switch to 4/6 CYLINDER position. Set DVOM on 20-volt AC scale. Start engine and measure voltage between diagnostic cable J30 (IDM detector) and J7 (BAT-) at breakout box. If input voltage pulses are present at IDM detector, output will be a square wave 5-7 volt AC signal. If output signal is 5-7 volts, go to step 2). If output signal is not 5-7 volts, go to step 3).
  2. Check IDM For Open To PCM  With ignition off, disconnect PCM. Disconnect ICM from diagnostic cable ICM tee. Leave EI diagnostic cable connected to wiring harness connector. Set DVOM on 200-ohm scale. Install a second breakout box to PCM wiring harness connector. Measure resistance between J41 (IDM I) at ICM breakout box and terminal No. 4 at PCM breakout box. If resistance is less than 5 ohms, PCM is not responding to IDM input. Replace PCM. If resistance is 5 ohms or greater, repair open in IDM circuit.
  3. Check IDM Output From ICM  With ignition off, set DVOM on 20-volt AC scale. Push and hold down IDM button at EI diagnostic cable connector (this opens IDM circuit to PCM). Start engine and measure voltage between J30 (IDM detector) and J7 (BAT-) at breakout box. If AC voltage is greater than 5 volts, go to step 4). If voltage is 5 volts or less, IDM output from module does not exist. Replace ICM.
  4. Check IDM For Short In PCM  With ignition off, disconnect PCM. Crank engine and measure voltage between J30 (IDM detector) and J7 (BAT-) at breakout box. If AC voltage is greater than 5 volts, PCM is loading IDM signal. Replace PCM. If voltage is 5 volts or less, go to step 5).
  5. Check IDM For Short To Power In Harness  With ignition off, set DVOM on 20-volt DC scale. With ignition on and engine off, measure voltage between J41 (IDM I) and J7 (BAT-) at breakout box. If DC voltage is less than 0.5 volt, go to step 6). If voltage is 0.5 volt or greater, IDM is shorted to power. Repair short circuit or replace harness.
  6. Check IDM For Short To Ground In Harness  With ignition off, disconnect ICM from diagnostic cable ICM tee. Leave EI diagnostic cable connected to wiring harness connector. Set DVOM on 20-k/ohm scale. Measure resistance between J41 (IDM I) and J7 (BAT-) at breakout box. If resistance is greater than 10,000 ohms, IDM is shorted to another wire between ICM and PCM. Repair short circuit or replace harness. If resistance is 10,000 ohms or less, IDM is shorted to ground. Repair short circuit.


  1. Check IDM Signal At ICM  With ignition off, install EI diagnostic cable to breakout box and ICM. DO NOT connect CKP sensor tee or coil tees. Use EI "8" overlay on breakout box. Connect EI diagnostic cable negative and positive leads to battery. Set EI diagnostic cable box switch to 8 CYLINDER position. Set DVOM on 20-volt AC scale. Start engine and measure voltage between diagnostic cable J30 (IDM detector) and J7 (BAT-) at breakout box. If input voltage pulses are present at IDM detector, output will be a square wave 5-7 volt AC signal. If output signal is 5-7 volts, go to step 2). If output signal is not 5-7 volts, go to step 3).
  2. Check IDM For Open To PCM  With ignition off, disconnect PCM. Disconnect ICM from diagnostic cable ICM tee. Leave EI diagnostic cable connected to wiring harness connector. Set DVOM on 200-ohm scale. Install a second breakout box to PCM wiring harness connector. Measure resistance between J41 (IDM I) at ICM breakout box and terminal No. 4 at PCM breakout box. If resistance is less than 5 ohms, PCM is not responding to IDM input. Replace PCM. If resistance is 5 ohms or greater, repair open in IDM circuit.
  3. Check IDM Output From ICM  With ignition off, set DVOM on 20-volt AC scale. Push and hold down IDM button at EI diagnostic cable connector (this opens IDM circuit to PCM). Start engine and measure voltage between J30 (IDM detector) and J7 (BAT-) at breakout box. If AC voltage is greater than 5 volts, go to step 4). If voltage is 5 volts or less, IDM output from module does not exist. Replace ICM.
  4. Check IDM For Short In PCM  With ignition off, disconnect PCM. Crank engine and measure voltage between J30 (IDM detector) and J7 (BAT-) at breakout box. If AC voltage is greater than 5 volts, PCM is loading IDM signal. Replace PCM. If voltage is 5 volts or less, go to step 5).
  5. Check IDM For Short To Power In Harness  With ignition off, set DVOM on 20-volt DC scale. With ignition on and engine off, measure voltage between J41 (IDM I) and J7 (BAT-) at breakout box. If DC voltage is less than 0.5 volt, go to step 6). If voltage is 0.5 volt or greater, IDM is shorted to power. Repair short circuit or replace harness.
  6. Check IDM For Short To Ground In Harness  With ignition off, disconnect ICM from diagnostic cable ICM tee. Leave EI diagnostic cable connected to wiring harness connector. Set DVOM on 20-k/ohm scale. Measure resistance between J41 (IDM I) and J7 (BAT-) at breakout box. If resistance is greater than 10,000 ohms, IDM is shorted to another wire between ICM and PCM. Repair short circuit or replace harness. If resistance is 10,000 ohms or less, IDM is shorted to ground. Repair short circuit.
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