Had code 188 ECT and 998 PCM in default. Could not get the 188 to clear even after changing the sensor, had 5 volts to sensor. Decided to check the return wire from the ECT to the computer. It went to the wrong connector and ended up a signal ground. I tracked pin 7 of the PCM and it went to the coolant temp sensor that is taped back in the harness for use on an electronic instrument panel. So I traced the rest and it turned out that the ECT sensor has never worked since this van was built. The wiring from the computer to the ECT actually went to coolant tem sensor that that wiring was going to th ECT. Completely reversed. Rewired the connectors and all the codes cleared. Something to beware off.