Dodgy sensor search

I have a query regarding the CTS on my 1997 Peugeot 106 1.0 TBI with the Bosch MA 3.1 management system. With the sensor unplugged and the ignition on, I only have 0.9 volts on the feed/yellow wire. The ATS and TPS both have 5 volts with the plug removed and ignition on.

My next move will be to check at the ECU, which I put off at first due to worry over removing the cover. If there is not 5V at the relevant pin there, can I splice off the ATS 5V to provide voltage to the CTS? The vehicle failed its emission test here in France, but in their wisdom they only give CO 0.34 and Lambda 1.034, with the only other reading given as fast idle CO 0.29. No gas readings at all!

One further thought, although I don’t think it’s relevant: the CTS has only one pin, but the plug to it has two. Mike I think you’re looking at the wrong sensor. The CTS is a twowire, two-pin sensor. Do you have any fault codes for the vehicle? Do you have the three-letter engine code? The engine code is CDZ. I only have a Sykes ACR2 with G2 suite, but it’s not Eobd-compatible and hasn’t recorded a fault. However, live data shows the engine temperature is not getting above 80°C and the O2 sensor is not switching (a new OE sensor is fitted). The injector duration is also not going below 2.4Ms. Could it be the thermostat? The O2 heater circuit is OK.

I have just rechecked those two sensors and the one with the green plug is a blue sensor with a 5V feed. The one with a single wire is the coolant warning light, I think.

I have a Crypton 4 Gas 290 for which I have just ordered a new oxy cell, so should be able to get readings in a week or so. I have just bought this car – now I know why it was so cheap! Mike Actually, 80°C is not low enough to cause your emissions failure. If the oxygen sensor is not switching, this could be the problem. Check the wiring circuit to it and, if it is OK, have the ECU tested. If the sensor is fine, then the ECU must be at fault. There was a small hole in the plastic elbow on the back of the SPI unit. It goes to the charcoal canister and has been repaired at some time. I also changed the O2 sensor, which was sooted up. All seems fine now. Mike