P00B7 Engine Coolant Flow Low

[EmmKay11945]

I was able to find this write-up from the Service Manual.

Nice, I will replace that and see what happens.

 

[New2the7]

Did you ever get to the bottom of this I have this -48 degree problem specified @ radiator outlet. I have replaced the G83 sensor which is located on the radiator pipe.

I am getting a weird reading with a voltmeter @ the connector for this sensor I'll attach pic. 133.0

But @ the other end of these wires (ECU end) I get a totally different reading 00.3 on pins #49&#29 on connector 91 @ the ECU

 

[Golffff]

The measurement at G83 was while the connector was plugged in? Removing the connectors at both ends should isolate if this wire pair is indeed continuous.

 

[New2the7]

I will do the test again tommorow. So I should have one or the other end of the wire connected and voltmeter on the other?

This may have been where I've gone wrong

Not the greatest with car wiring

 

[Golffff]

Disconnect both connectors and do continuity from one wire (connector to connector), then the other wire (should show short), and then between both wires on each connector (should show open). Also, it shows on the diagram that the G83 sensor is purely resistive but maybe use a hair drier to warm it up and check that resistance changes between the 2 pins on the sensor, to confirm it's simply resistive.

 

[New2the7]

If I have understood correctly

I have just done one wire from each end of the connector and I get a reading of around 15 ohms. The strange thing is it doesn't matter if I keep one prob on one end of a connector but change the probe to the other wire on the other end the reading is still around 15.

Or does that sound correct as the sensor is just resistive as you say. (I have heated it up and the reading goes up)

@ the ECU end when I put the probes on each connection there I get the 0.03 reading.

But @ the sensor end I still get the 133.0 reading.

 

[Golffff]

So according to the official wiring diagram, the G83-1 to T91(ECM)-49 is Black wire, and G83-2 to T91(ECM)-29 is a Brown wire. If you're not getting close to 0ohm on the ends of these wires, that's unexpected.

 

[New2the7]

If I have understood correctly

I have just done one wire from each end of the connector and I get a reading of around 15 ohms. The strange thing is it doesn't matter if I keep one prob on one end of a connector but change the probe to the other wire on the other end the reading is still around 15.

Or does that sound correct as the sensor is just resistive as you say. (I have heated it up and the reading goes up)

@ the ECU end when I put the probes on each connection there I get the 0.03 reading.

But @ the sensor end I still get the 133.0 reading.

I have just done the same test again strangely and I get 0.00 so I don't know how I managed to get the reading of 15

Also I have done the continuity test from the connector which goes to g83 and the corresponding pins on T91 and I get no beep for continuity.

But if I do the same test for the other temp sensor G62 in the cylinder head and the corresponding pins on T105 I get a beep for continuity.

But I have also found that if the battery is connected (ECU plugs still plugged in) the reading I get @ the connector for G83 becomes 0.00 instead of the 133.0

Should I have had the battery connected to perform all of these tests??

I don't dare have the battery connected whilst the ECU unplugged.

 

[Golffff]

I agree that these days it's probably less problematic when removing a large number of sensors at once to disconnect the battery (or remove the ECM fuse, I don't know which it is off hand). Continuity can only be proved when there's no interference from other circuitry (like the ECM).

 

[MrBxx]

Hi guys,

Do you happen to get to the bottom of your issue please? I am having same P00B7 code for cooling flow and have got the below readings from vcds, car goes into limp mode and the temperature gauge rises above 90c, all is well once the car is switched off and on.

IDE00025 Coolant temperature 13 °C
IDE00187 Coolant temperature at engine start 12.7 °C
IDE00192 Coolant temperature at radiator outlet: actual value 14.0 °C
IDE00193 Coolant temperature at engine outlet: specified value 13.5 °C
IDE00194 Coolant temperature at radiator output: specified value -48.0 °C
IDE00195 Coolant temperature difference between engine and radiator 0.0 °C
IDE03377 Coolant temp at radiator output: unconditioned voltage 3.787 V
IDE06396 Coolant temperature at engine outlet: unconditioned voltage 3.811 V

Is the -48c anything for concern do you think, i am starting to sway towards replacing the thermostat/water pump housing as they fail so often.

Thank you

 

[Golffff]

Well steamy weather has returned and ..... the problem appears to be gone (for now).

What changed?

I replaced the car battery over the winter after the cranks kept getting slower (it was ~4y old). Might be worth checking the battery voltage when the engine is off and the water pump is recirculating.