PBP projects for R/C models

[Kenjones1935]

Ladies and Gentlemen:

My project and I have a problem. PULSIN is putting zero into its target register even though my PICkit 2 LOGIC TOOL sees a reasonable pulse. See picture, below.

It is happening on the inputs from both SRF05 proximity detectors. My code, below, looks for zero and blinks some LED's if it sees a zero. They blink on the very first proximity tests.

Any suggestions? Is my code incorrect? Are there vulnerabilities or idiosyncrasies of which I should be aware?

symbol trigright = PORTB.0 ' Define output pin for Trigger pulse
symbol trigfront = PORTB.1 ' Define output pin for Trigger pulse

symbol echoright = PORTB.2 ' Define input pin for Echo pulse
symbol echofront = PORTB.3 ' Define input pin for Echo pulse

puls:
GOSUB blinkloop0
DEFINE PULSIN_MAX 65535
pulsout trigright,2 ' produce 20uS trigger pulse (must be minimum of 10uS)
pulsin echoright,1,rangeright ' measures the range in 10uS steps

pulsf:

pulsout trigfront,2 ' produce 20uS trigger pulse (must be minimum of 10uS)
pulsin echofront,1,rangefront ' measures the range in 10uS steps
pause 10 ' recharge period after ranging completes

'*****test for zeros******
IF rangeright = 0 then
gosub blinkloop45
endif
if rangefront = 0 then
gosub blinkloop67
endif
return