Two weeks ago I was getting a P0236 - Turbocharger Boost Sensor A Circuit Range/Performance. I cleared it a few times and it kept coming back. It's been about a week since I last checked for codes, and now I've got a P0237 - Turbocharger Boost Sensor A Circuit Low. I did some troubleshooting on the MAP sensor last weekend but I couldn't perform a few of the checks because I didn't have the necessary equipment on hand. What is the difference between these two codes? Does the 0237 mean that the frequency of the output signal is too low? Here's what I have done so far to check the sensor:

15psi pressure gauge read 11-12 psi in 2nd gear at 3000rpm up a steep hill with gauge plumbed into MAP hose.

Key off checks on MAP connector:
A-GND: 0.3 Ohms
B-GND: 724 Ohms
C-GND: 5500 Ohms

Key on checks on MAP connector:
A-GND: 0.006VDC
B-GND: 5.07VDC
C-GND: 5.07VDC

MAP output signal was 109.3Hz with key on, engine off.

I did not check the output with 10psi applied to the MAP hose. I think I've got a good high precision, low pressure regulator and gauge at work I can use with a shop air line or air tank to put 10psi to it and repeat the signal check. I can also use this setup to verify the accuracy of the pressure gauge I used in the above test. I'll also double check the KOEO output signal. I also tightened the hose clamps on the intake boots, but I guess I'll pull them and check for leaks.

Are there any other checks to perform? Am I missing anything else?

 

Skeeter, Maybe it's in the harness. I'ts about the only thing you haven't checked yet. Below is from the repair manual, but it is done with a breakout box. .

HARNESS RESISTANCE CHECKS
(CHECK WITH BREAKOUT BOX INSTALLED ON ENGINE HARNESS ONLY)

Test Points Spec. Comments
No. 91 to A <5 ohms Sensor connector to 104 pin connector.
No. 90 to B <5 ohms Sensor connector to 104 pin connector.
No. 34 to C <5 ohms Sensor connector to 104 pin connector



If you get the test above done the next step, below, in trouble shooting requires another special tool. You may need to go to the stealership or find someone with the specialty tools.


KOEO DIAGNOSTIC TROUBLE CODE (DTC) 0237 OR 0235

• DTC 0237 (1996 model year) indicates turbo boost sensor A circuit low input.
• Possible causes:
  • MAP signal circuit open, shorted to ground, shorted to B+ , or shorted to VREF
  • Open or shorted VREF circuit
  • Open or shorted signal return circuit
  • Damaged MAP sensor
  • Damaged PCM
• Key off.
• Disconnect MAP sensor connector.
• Connect the MAP sensor tester between the vehicle harness connector and the MAP sensor.
• Insert the MAP tester banana plugs into a DVOM. Note: Green light on tester indicates VREF is OK (4.5-5.5 volts) and signal return is OK. Red light indicates VREF is either too low or too high. No lights indicate VREF or signal return are open or shorted.
  
  
• Key on.

 

Anyone in the Seattle area have the 104 pin breakout box they'd be willing to lend for the weekend? Thanks.

 

A breakout box is usually a dealer only thing, but IIRC the Autoeninuity or Ease scanner will give some of this info on your PC.

http://autoenginuity.com/
http://obd2.com/scantool/scantool.htm

My AE is on the way, can't wait

BTW: they are both code readers too.

 

Yeah I was going to order the AE on Tuesday when ITP is open.

 

I am very new here, but have the same code being thrown now that I just installed a Bully Dog Outlook Monitor on my '02 PSD F-250. Could it be something as simple as a bad connection in the harness or at the plug? Essentially, the installation of the outlook involves unplugging the stock MAP sensor plug and plugging it back into a "Tee" connector which gives the outlook monitor it's power and readings. I'm hoping it's just a dirty connection and not something I messed up.

 

You will get more help in the correct forum.

https://www.ford-trucks.com/forums/f...splay.php?f=31